Uncooled Infrared Photon Detection Concepts and Devices

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Physics and Astronomy Dissertations Department of Physics and Astronomy

3-23-2009

Viraj Vishwakantha Jayaweera Piyankarage

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Recommended Citation Piyankarage, Viraj Vishwakantha Jayaweera, "Uncooled Infrared Photon Detection Concepts and Devices." Dissertation, Georgia State University, 2009. https://scholarworks.gsu.edu/phy_astr_diss/30

This Dissertation is brought to you for free and open access by the Department of Physics and Astronomy at ScholarWorks @ Georgia State University. It has been accepted for inclusion in Physics and Astronomy Dissertations by an authorized administrator of ScholarWorks @ Georgia State University. For more information, please contact [email protected]. UNCOOLED INFRARED PHOTON DETECTION CONCEPTS AND DEVICES

VIRAJ VISHWAKANTHA JAYAWEERA PIYANKARAGE

Under the Direction of Unil Perera

ABSTRACT

This work describes infrared (IR) photon detector techniques based on novel semiconductor device concepts and detector designs. The aim of the investigation was to examine alternative IR detection concepts with a view to resolve some of the issues of existing IR detectors such as operating temperature and response range. Systems were fabricated to demonstrate the following IR detection concepts and determine detector parameters: (i) Near-infrared (NIR) detection based on dye-sensitization of nanostructured semiconductors, (ii) Displacement currents in semiconductor quantum dots (QDs) embedded dielectric media, (iii) Split-off band transitions in GaAs/AlGaAs heterojunction interfacial workfunction internal photoemission (HEIWIP) detectors. A far-infrared detector based on GaSb homojunction interfacial workfunction internal photoemission (HIWIP) structure is also discussed. Device concepts, detector structures, and experimental results discussed in the text are summarized below.

Dye-sensitized (DS) detector structures consisting of n-TiO2/Dye/p-CuSCN heterostructures with several IR-sensitive dyes showed response peaks at 808, 812, 858, 866, 876, and 1056 nm at room temperature. The peak specific-detectivity (D*) was 9.5×1010 cm Hz-1/2 W-1 at 812 nm at room temperature. Radiation induced carrier generation alters the electronic polarizability of QDs provided the

quenching of excitation is suppressed by separation of the QDs. A device constructed to illustrate

this concept by embedding PbS QDs in paraffin wax showed a peak D* of 3×108 cm Hz1/2 W-1 at

~540 nm at ambient temperature.

A typical HEIWIP/HIWIP detector structures consist of single (or multiple) period(s) of doped emitter(s) and undoped barrier(s) which are sandwiched between two highly doped contact layers.

A p-GaAs/AlGaAs HEIWIP structure showed enhanced absorption in NIR range due to

heavy/light-hole band to split-off band transitions and leading to the development of GaAs based

uncooled sensors for IR detection in the 2-5 µm wavelength range with a peak D* of 6.8×105 cm Hz1/2 W-1.

A HIWIP detector based on p-GaSb/GaSb showed a free carrier response threshold wavelength at

97 µm (~3 THz)with a peak D* of 5.7×1011 cm Hz1/2 W-1 at 36 µm and 4.9 K. In this detector, a

bolometric type response in the 97 - 200 µm (3-1.5 THz) range was also observed.

INDEX WORDS: Infrared detectors, Photon detection, NIR detectors, THz detectors, Uncooled detectors, Dye-sensitized, IR dye, Quantum dot, Split-off band, GaSb, GaAs, AlGaAs, TiO2, CuSCN, PbS, Homojunction, Heterojunction, Workfunction, Photoemission, Displacement currents, 1/f noise. UNCOOLED INFRARED PHOTON DETECTION CONCEPTS AND DEVICES

VIRAJ VISHWAKANTHA JAYAWEERA PIYANKARAGE

A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of

Doctor of Philosophy

in the College of Arts and Sciences

Georgia State University

2009

VIRAJ VISHWAKANTHA JAYAWEERA PIYANKARAGE

Major Professor: Unil Perera

Committee: Vadym M. Apalkov Douglas Gies Xiaochun He Kirthi Tennakone Brian D. Thoms

Electronic Version Approved:

Office of Graduate Studies College of Arts and Science Georgia State University May 2009 DEDICATION

To my parents and teachers

iv ACKNOWLEDGEMENTS

I would like to express my deepest sense of gratitude to my supervisor Prof. Unil Perera for his patient guidance, encouragement and excellent advice throughout this study. His constant enthusiasm, support, and invaluable suggestions made this work successful. He has been everything that one could want in an advisor. Next, I am grateful to my co-supervisor, Prof. Kirthi

Tennakone, who introduced me to the research field and has been abundantly helpful and offered invaluable assistance, support, and guidance. Deepest gratitude is also due to the members of the supervisory committee: Dr. Vadym M. Apalkov, Dr. Douglas Gies, Dr. Xiaochun He, and Dr.

Brian D. Thoms for fruitful discussions, technical assistance, and effort in reading and providing me with valuable comments on this dissertation. I would like to convey special acknowledgement to Dr. Steven Matsik, who was always open for questions and discussions relating theoretical work and his valuable scientific advice. Special thanks to post doctoral associate Dr. Gamini

Ariayawansa, former members Dr. Mohamed Rinzan, and Dr. Aruna Weerasekara for valuable discussions on the subject matters. I would also like to thank present colleagues in the group:

Ranga Jayasinghe, Dulipa Pitigala, Laura Byrum, Greggory Rothmeier, Jiafeng Shao, and Dr.

Manmohan Singh. I wish to thank all the individuals of the Department of Physics and Astronomy, especially the Physics workshop team headed by Mr. Charles Hopper who converted my mechanical drawings into physical reality, and friends for their contribution, friendship, love, and

helps. Finally, I take this opportunity to express my profound gratitude to my beloved parents,

parent in law, and my wife for their moral support and patience during my study at GSU.

v TABLE OF CONTENTS

ACKNOWLEDGEMENTS v

LIST OF TABLES ix

LIST OF FIGURES x

LIST OF ABBREVIATIONS xvi

Chapter 1 Introduction ...... 1

Chapter 2 Dye-sensitized near-infrared room-temperature photovoltaic photon detectors and 1/f noise in semiconductor nanostructures...... 8 2.1 DS photon detectors...... 8 2.1.1 DS IR detector fabrication ...... 9 2.1.2 Experimental results and discussion...... 11 2.1.3 Conclusion and future possibilities...... 15 2.2 1/f noise in DS photon detectors and photovoltaic cells ...... 19 2.2.1 Introduction ...... 19 2.2.2 Frequency dependent noise...... 20 2.2.3 Sample preparation and experimental setup for noise measurements ...... 21 2.2.4 Results and discussion...... 23 2.2.5 Conclusion...... 28

Chapter 3 Displacement currents in colloidal quantum dots embedded dielectric media: A method for room temperature photon detection...... 29 3.1 Introduction...... 29 3.2 PbS colloidal quantum dot (CQD) preparation and detector fabrication...... 30 3.3 Detection mechanism, results, and discussion...... 31 3.4 Conclusion ...... 37

Chapter 4 Split-off transition based uncooled infrared detectors for 3-5 µm and beyond...... 39 4.1 Introduction...... 39 4.2 Heterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) detectors...... 41 4.3 Split-off band detector mechanism ...... 43

vi 4.4 Split-off response of HEIWIP detectors designed for MIR ...... 45 4.5 Uncooled split-off detector design and experimental results ...... 49 4.6 Long wavelength (MIR and FIR) response observed in the split-off detectors ...... 56 4.7 Future Work...... 61 4.7.1 Proposed materials for split-off threshold extension...... 61 4.7.2 Dual-band detector design for the 3-5 and 8-14 µm atmospheric windows...... 67 4.8 Conclusion ...... 70

Chapter 5 GaSb homojunctions for Far-IR (THz) detection ...... 72 5.1 Introduction...... 72 5.2 GaSb homojunction detector mechanism ...... 73 5.3 Experimental Design ...... 73 5.3.1 Dark current, responsivity and noise measurements...... 74 5.4 Results and discussion...... 74 5.5 Conclusion ...... 82

Chapter 6 Summary and conclusion...... 85

BIBLIOGRAPHY 90

Appendix A Detector characterization ...... 112 A.1 Responsivity (Photo Sensitivity) ...... 112 A.1.1 Spectral response measurements and responsivity calibration ...... 112 A.2 Quantum efficiency (η) ...... 113 A.3 Noise Equivalent Power (NEP) ...... 114 A.4 Specific Detectivity (D*)...... 115 A.4.1 Noise measurements and detectivity calculation...... 115

Appendix B Software development with Microsoft Visual Basic ...... 117 B.1 Multi-sample I-V-T characterization software...... 117 B.1.1 I-V-T setup instrument configuration ...... 118 B.1.2 User interfaces of the I-V-T software ...... 120 B.1.3 Flow chart for the IV opration mode ...... 129 B.1.4 Flow chart for the multi sample IVT operation mode...... 130 B.1.5 Source code...... 131 B.2 UV-VIS-NIR detector spectral response characterization software...... 185 B.2.1 UV-VIS-NIR setup instrument configuration ...... 186

vii B.2.2 User interfaces ...... 188 B.2.3 Flow chart for the spectral responsivity (UV-VIS-IR) measurement (Spectral Products monochromator) ...... 195 B.2.4 Source code...... 197 B.3 Noise spectrum analyzer software ...... 258 B.3.1 Instrument configuration of the noise measurement setup...... 259 B.3.2 User interfaces ...... 260 B.3.3 Source code...... 262 B.4 x-z-θ stage controller...... 302 B.4.1 User interface...... 304 B.4.2 Source code...... 305

Appendix C Microsoft Excel macro programs development for data file manipulation ...... 317 C.1 I-V-T data import and Arrhenius data extracting...... 317 C.1.1 Excel macro source code...... 319 C.2 FT-IR Spectrum data import and responsivity calculation ...... 323 C.2.1 Excel macro source code...... 325

viii LIST OF TABLES

Table 2.1 Responsivities (R) of the detectors at peak absorption wavelengths (λmax) of different sensitizers...... 16

Table 2.2 The values of parameters A, δ and γ for different systems obtained by fitting -4 noise data with formula (2.3), biasing voltage = 18 V, and Io = 3.2×10 A...... 27

Table 4.1 Sample parameters at optimum operating temperatures (Tmax). The dynamic resistance (RDyn), darkcurrent density (IDark) at 1V bias, and D* were experimentally measured. ∆L/H is the designed band offset...... 54

Table 4.2 The Split-off band offset energy for different materials. Nitride and phosphide compounds are of interest for wavelengths beyond 10 µm. The split-off energy of the quaternary alloy InGaAsP can be varied from 110 - 379 meV by changing the As fraction...... 62

Table 6.1 A summary of selected detectors demonstrated in this work along with their specifications. λp, λRange, Rp, D*, and T stand for peak wavelength, response wavelength range, peak responsivity, specific detectivity, operating temperature respectively...... 86

ix LIST OF FIGURES

Figure 2.1 Cross-section of the DS NIR detector. Here CTO denotes the conducting tin oxide layer that is transparent to VIS and NIR. The schematic exaggerates the TiO2 surface in order to clearly show the roughness of the layer...... 10

Figure 2.2 An energy level diagram showing the band edge positions of n-TiO2, p-CuSCN and ground (So – positioned arbitrarily) and excited (S*) states of the dye...... 12

Figure 2.3 Spectral responsivity of the heterojunctions (a) n-TiO2/IR820/p-CuSCN (b) n- TiO2/BPR-IR820/p-CuSCN (c) n-TiO2/IR783/p-CuSCN (d) n-TiO2/MC-IR792/p-CuCSCN (e) n-TiO2/IR820-IR1040/p-CuSCN (f) n-TiO2/BPR-IR1040/p-CuSCN...... 14

Figure 2.4 Power spectral density of the dark current noise of the hetrojunction n- TiO2/MC-IR792/p-CuSCN...... 18

Figure 2.5 A schematic diagram illustrating sample geometry used for the noise measurement. The electrical connectivity of a conducting tin oxide (CTO) glass sheet (1.5 × 2 cm2, sheet resistance 12 ohm/square) was broken by scribing a line (~8 µm thick) with a diamond pointer. A layer of colloidal TiO2 (thickness ~12 µm) was screen printed above the scribe and sintered at 430 ºC for 30 minutes...... 22

Figure 2.6 The experimental set up used for noise measurements. The sample is mounted in an enclosure provided with facilities for evacuation, introduction of different gasses/vapors, and heating, and the sample is connected in series with a 56 kΩ resistor (R) and 18 V battery pack. A low noise preamplifier amplified the voltage fluctuations across the sample, and a power spectrum analyzer was used to obtain the spectral power density S(f)...... 24

Figure 2.7 Noise spectra at 23 °C of, (a) bare TiO2 film in N2. (b) bare TiO2 film in N2 at RH ~70 %. (c) bare TiO2 in a N2 saturated with I2 vapor. (d) TiO2/BPR in N2. (e) TiO2/N3 in N2. (f) TiO2/BPR in N2 saturated with I2. (g) TiO2/N3 in N2 saturated with I2. (h) TiO2/BPR in N2 at RH ~70 %. (i) TiO2/N3 in N2 at RH ~70%. (j) TiO2 (vacuum) (k) TiO2/BPR (vacuum) (l) TiO2/N3 (vacuum)...... 26

Figure 3.1 (a) Absorption spectrum of the suspension of PbS colloidal quantum dots (CQD). (b) A cross section of the CQD embedded detector experimentally tested. The thickness of the CQD embedded paraffin wax layer is s ~ 10 µm...... 32

Figure 3.2 The equivalent circuit of the detector (inside the dashed box) and the circuit used for measurement of the photoresponse (Cd = detector capacitance, Rd = detector resistance)...... 35

Figure 3.3 The responsivity of the detector under different bias voltages. (85 MΩ resistor was used as Load resistor RL and chopping frequency was 57 Hz)...... 36

Figure 4.1 (a) Typical structure of a GaAs emitter AlGaAs barrier HEIWIP detector. (b) Band diagram showing the workfunction (∆) for photoemission of carriers. Here, ∆ is

x given by ∆ = ∆d + ∆x where ∆d and ∆x are the contributions from the doping and the Al fraction, respectively. The dashed lines indicate the valence-band edge if the barriers were GaAs...... 42

Figure 4.2 A band diagram for an emitter region of the detector, illustrating the different IR detection threshold mechanisms. The horizontal dashed lines EB-L/H and EB-SO indicate the L-H/H-H and split-off band maximum (k=0) positions in the barrier. The horizontal dotted lines EF and EE-SO indicate the Fermi energy and the split-off energy in the emitter at k=0. The arrows indicate the possible threshold transition mechanisms (1) direct transition from L-H band to SO band followed by scatter back to L-H band (2) indirect transition followed by scatter back to L-H band...... 44

Figure 4.3 A schematic of a mesa of the processed detector showing the window etched in the top contact for front-side illumination. The number of emitter barrier periods, emitter and barrier thickness, and doping values were different for each design. Part of the bonded contact wires are also shown here...... 47

Figure 4.4 Measured responsivity of HE0204 at temperatures from 80 K to 130 K under 5 kV/cm bias. The responsivity increased up to 105 K and then started to decrease. The peak response was 0.55 mA/W at ~2.0 µm. The two steps indicated by arrows in the response at 2.8 µm and 3.4 µm are due to the thresholds for mechanisms (1) and (2), respectively...... 48

Figure 4.5 The calculated absorption coefficient for the free carrier and the SO band mechanisms in a 3×1018 cm-3 p-doped GaAs layer...... 50

Figure 4.6 Measured absorption for the sample HE0204 showing an increased absorption from the split-off transitions. The dashed line shows the expected free carrier response varying as a λ2...... 51

Figure 4.7 The dark current density vs. temperature for samples SP1, SP2 and SP3 under 1V applied bias. The samples SP1, SP2, and SP3 have barriers with Aluminum fractions 0.28, 0.37, and 0.57, respectively. The dark current densities reached ~1 A/cm2 for each sample at 140, 190, and 300 K. Those temperatures were properly matched with the experimentally observed, optimum operating temperatures for each sample...... 53

Figure 4.8 The responsivity of the samples SP1, SP2 and SP3 at the optimum operating temperatures of 140 K, 150 K and 300 K, showing peaks around 2.6 µm. The applied bias was 4 V for all three measurements...... 55

Figure 4.9 The measured responsivity of the sample SP3 under 4 different biases at 300 K showing peaks around 2.5 µm. The arrows 1 and 2 indicate the thresholds at 2.9 µm and 3.4 µm corresponding to the transitions 1 and 2 shown in Figure 4.2. The inset shows the responsivity of the samples SP1 and SP2 at 140 K and 150 K, respectively...... 57

Figure 4.10 The responsivity of the samples SP1, SP2 and SP3 at 140 K, 150 K and 150 K, respectively. The higher responsivities seen for the longer wavelength threshold samples (SP1 and SP2) are possibly due to impact ionization (gain), compared to the shorter threshold sample (SP3)...... 58

xi Figure 4.11 The responsivity of the split-off detector SP3 in the 2 to 20 µm range for different bias values in the 1- 5 V range. (a) At 330 K temperature, the maximum long wavelength response was ~800 mV/W for a bias of 5 V. Peak responsivity of the split-off range was ~475 mV/W at same bias. (b) At 250 K temperature the maximum long wavelength response was ~1250 mV/W and split-off responsivity was 3000 mV/W for a bias of 5 V. The response was nearly constant over most of the range...... 60

Figure 4.12 Band gap and lattice constant of selected III-V semiconductors (data were taken from “Handbook series on semiconductor parameters111”.) Solid lines represent direct band region and dashed lines represent indirect band region. GaP/AlGaP would be a high- quality, lattice matched system similar to GaAs/AlGaAs. Also, InGaAs and InGaP can be lattice matched to InP and GaAs, respectively...... 64

Figure 4.13 The variation of the valence band offset energy (∆EV) and split-off energy (ESO) of the In1-xGaxAsyP1-y/InP heterostructure with Arsenic fraction y. To achieve a similar or 10% less ∆EV, the Arsenic fraction should be in the 0.5 - 0.7 range...... 65

Figure 4.14 Schematics of the In1-xGaxAsyP1-y emitter and Al0.3Ga0.7As barrier based detector structure, which is lattice matched to the GaAs substrate...... 66

Figure 4.15 Proposed dual-band detector structure for the 3-5 and 8-14 µm atmospheric windows. A three-contact design will allow the separate detection of 3-5 µm radiation from the top to middle contact (TC – MC) and 8-14 µm range radiation from the middle to bottom contact (MC – BC). The Al fractions of the barrier (0.57 and 0.8) were, selected so that the barrier height is equal to the split-off energy of the emitter layer...... 68

Figure 4.16 The band diagram of the proposed dual-band detector under a biased condition. The middle contact (MC) is negatively biased, while the top (TC) and bottom contacts (BC) are positively biased...... 69

Figure 5.1 (a) Schematic drawing of the processed detector and (b) an energy-band diagram with the detection mechanism of the device under forward bias. The internal work function ∆ originates from the doping offset between the emitter and the barrier. Here ∆EV is the valence-band-edge offset at the p+ and undoped interface...... 75

Figure 5.2 The dark current density vs. bias voltage for 8 different mesas in sample GSU- A3 measured at 10 K shows good uniformity of the structure. A single dark IV curve for one mesa at the 4.9 K spectral measurement temperature is also shown...... 76

Figure 5.3 Spectral response as measured at 4.9 K for sample GSU-A3 under different forward bias voltages. The 20 to 43 µm range responsivity has a peak responsivity of 9.7 A/W at 36 µm and 3.7 V bias...... 78

Figure 5.4 The full spectrum including the long wavelength response at 1, 2 and 3 V bias conditions. Note that the response is plotted in a log scale in order to emphasize the long wavelength response. The arrow shows the 97 µm free carrier response threshold wavelength position. The noise curves at the bottom were taken by blocking the FTIR

xii source beam and the dashed line shows the maximum noise level of the spectral response measurement setup...... 79

Figure 5.5 Arrhenius curve of the sample showing slope of -157.2. The internal workfunction ∆ of 12.8 ± 0.3 meV was calculated using this slope...... 81

Figure 5.6 The bias dependence of the peak responsivity at 4.9 K. The responsivity was almost linear (with a slope of 1.61 ± 0.06 A/WV) for low biases (< 2.5 V)...... 83

Figure B.1 The block diagram of the I-V-T setup showing GPIB communication connections (red lines with arrowheads) and other sample wirings (blue lines)...... 118

Figure B.2 Photograph of the IVT setup showing Keithley 2400 source meter, 7001 switch system, SI-9620 temperature controller (top) and helium closed cycle refrigerator (bottom)...... 119

Figure B.3 The initializing window searches communication status of all three instruments in order to initialize GPIB communication. If a communication error occurs or instrument is not physically connected, it will inform the user to check the particular instrument and connections...... 120

Figure B.4 The main program window showing manual I-V mode operation settings. In this mode user can select the samples by clicking the buttons labeled A to J and enter scan parameters and a temperature. The “Settings” tab and “Graph (log)” tab views are shown in the figure...... 121

Figure B.5 The user interface for the I-V mode settings. By clicking different tabs in the top of the window the user can view different graphs such as the I-V plot on log scale, I-V plots on a linear scale, or an I-t plot for each voltage...... 122

Figure B.6 User interface for the multi sample I-V-T scan setup. In this mode user can select the samples to be tested (labeled as A-J), voltage range, temperature range… etc. When a scan is started, the program will set the starting temperature. After it reaches the specified temperature, it will switch samples one at a time and record I-V curves. This process is repeated at each specified temperature...... 123

Figure B.7 The I-V-T mode main screen showing the active sample graph in the left window and the sample temperature variation with the time in the right window...... 124

Figure B.8 The temperature vs. time plot for the I-V-T mode. Red circles indicate the measurement starting point...... 125

Figure B.9 The control panel for the Keithley 2400 source meter. The user can use this to find scanning voltage limits based on a specified current level for their samples...... 126

Figure B.10 The control panel for the SI9620 temperature controller. This can be used to observe live temperatures close to the sample (T2), close to the heating element (T1) and the actual heater power (H). The user also can set the temperature to a specific value by entering a value to “setpoint”. Three constants (proportional term, integral term, and

xiii derivative term) can also be changed that the temperature controller algorithm needs to determine the heater power...... 127

Figure B.11 This panel controls the Keithley 7001 switch system and can be used as standalone software. By clicking corresponding button, the user can connect the corresponding sample (A – J) to a measuring instrument (source meter, volt meter, preamplifier... etc.). The switch system is wired in four wire configurations to allow the user a to use wide variety of instruments which have four inputs (two wires to apply current and two for measuring voltage) or two inputs...... 128

Figure B.12 Block diagram of the UV-VIS-NIR detector characterization system...... 186

Figure B.13 Photograph of the UV-VIS-NIR detector characterization system...... 187

Figure B.14 Hardware initialization window. At the starting step of the program, it will search availability of all the instruments and communication status, power up the stepper motor controllers, find the zero position for the stepper motor controlled mirror and sample-stage, and check the shutter status. If successful, this window will automatically disappear, otherwise it shows an error message asking the user to check the status of the particular instrument...... 188

Figure B.15 The main user interface of the UV-VIS-NIR detector characterization software. There are three different user selectable working modes: (i) regular spectrometer mode for absorption and reflection measurements, (ii) light intensity calibration mode, and (iii) custom detector characterization mode. The user can observe the real time raw spectrum, responsivity (V/W), and incident light intensity for the custom detectors...... 189

Figure B.16 The “monitor-mode” control panel allows the user to control all the instruments, motors and stages manually through the software. The user can change the lock-in-amplifier and monochromator parameters, properly align the detectors, and real time observe the output of the selected detector at a selected wavelength, upon the selection of a light source and a filter...... 190

Figure B.17 The “Advanced setup” control panel allows the user to change the hardware configurations such as wavelength range for each grating, wavelength position for each filter, wavelength ranges for each light source and the standard detectors (Si and InGaAs). Grating efficiency curves for all available gratings are inserted on the top of the panel so that user can easily determine which grating is most suitable in the wavelength region of interest. Users can save their own configuration settings, and they can also restore the original settings by pressing the “Restore Default Settings” button...... 191

Figure B.18 A view of the “stepper motor position settings”. This is another advanced user interface that allows the user to set the light-source-selecting-mirror positions and detector mounting stage positions. The numbers represent the actual number of steps from the zero position of the each stepper- motor. After a hardware modification, such as adding a new sample mount to the custom detector slot, the user can configure the new position and save it for future use...... 192

xiv Figure B.19 The chopper control panel allows the user to set the chopper frequency to one of the preset values or any other custom value. The user can observe the current frequency on the screen...... 193

Figure B.20 The Lock-in-Amplifier control panel allows the user to change the lock-in amplifier settings and display different components of the output value such as the real part (x), imaginary part (y), phase angle (θ), and magnitude of the output (R). As an optional feature, the user can change the output voltage (-10 V to 10V) of the three auxiliary ports located in the back panel of the lock-in-amplifier...... 194

Figure B.21 Block diagram of the noise measurement setup. The sample, a power supply (battery), a bias resistor, and a low noise preamplifier are placed inside the noise-shielding cage. The sample is mounted in the same dewar system which is used for spectral measurements. A thick copper plate at the sample temperature is used as the radiation block to provide dark conditions for the detector...... 259

Figure B.22 The main user interface for the noise spectrum analyzer software showing real experimental data taken from the samples...... 260

Figure B.23 Spectrum analyzer control panel. On screen buttons allow the user to change the parameters remotely without using the instrument front panel buttons...... 261

Figure B.24 Photgraphs of the x-z-θ stage (top) showing moving directions and placement in the FTIR sample compartment and (bottom) a closer view of the mechanical parts...... 303

Figure B.25 The user interface of the x-z-θ stage controller software. The program allows the user to move the sample stage by clicking on-screen buttons, using keyboard arrow keys, or directly entering the new location coordinates. The user can save the locations and easily repeat the measurements on saved locations...... 304

Figure C.1 Inserted custom menu showing the items “Import IVT Data” and “Arrhenius data extracting”. “Import IVT Data” allows the user to import a large number of data files at once and automatically plot the data. The second item allows the user to extract Arrhenius data (See Appendix A) and save it in sheet 2 of the Excel work book...... 318

Figure C.2 Custom menu item “Spectrum” inserted in to the Excel menu allows user to: format workbook, import multiple spectrum data files, plot data, import bolometer data file, calculate responsivity. The last option can be used to import multiple data files and calculate reflection/transmission with a selected background curve...... 324

Figure C.3 The user interface of the spectral calculator macro program. The “Browse” button can be used to open Multiple sample spectra files and one background spectra file. Pressing the “Calculate Ratio” button will start copying sample data into the Sheet 1, write the calculated data into the Sheet 2 of the Excel work book, and plot the final graph...... 338

xv LIST OF ABBREVIATIONS

BLIP background kimited performance

BPR bromopyrogallol red

CB conduction band

CQD colloidal quantum dot

CTO conducting tin oxide

CUSCN Copper thiosinate

DS dye-sensitized

DSN dye-sensitization

DSNIRPDs Dye-sensitized near infrared photon detectors

DSSCs dye-sensitized solar cells eV electron volts

FDN frequency dependent noise

FFT Fast Fourier Transform

FIR far-infrared

FT-IR Fourier-transform infrared

GDSSCs Gratzel type solar cells

HEIWIP heterojunction interfacial workfunction internal photoemission

H-H heavy hole

HIWIP homojunction interfacial workfunction internal photoemission

IR Infrared

L-H light hole

xvi MC mercurochrome

N3 cis-dithiocyanatobis (4-4’-dicarboxylic acid-2, 2’Ru[II])

NEP Noise Equivalent Power

NIR near-infrared

QDs Quantum dots

RH relative humidity

TEC thermo-electric-coolers

THz Terahertz

TiO2 Titanium dioxide

UV ultraviolet

VB valence band

xvii Chapter 1

Introduction

Humans and most animals have five senses: sight, hearing, taste, smell, and touch as avenues for

observing the environment. Nature has given us one of the world’s best visible cameras (equivalent

to ~576 megapixels1,2), our eyes. Our skin is sensitive to infrared (IR) radiation. Some animals such as rattlesnakes3 and pit vipers4 are specialized in IR sensing. Their IR sensory organs can

readily identify warm-blooded prey they need to hunt quickly. Nature invented these precision IR

detection techniques millions of years ago; man noticed the presence of an invisible heat. In 1800,

Sir Frederick William detected IR radiation using a thermometer5,6. Man-made contraptions have enabled expanding the region of detectability of the electromagnetic radiation beyond the short and long wavelength limits. In IR detectors, the radiation incident on a probe is converted to a signal readily accessible to the human senses. As an example, night vision IR imaging cameras assign visible colors that are proportional to the temperature of the object (or IR energy received by each tiny mesa (pixels) on the detector array). Eventually a night vision camera produces an image on a screen that the human brain can identify based on eyesight.

The IR region is one of the most interesting bands in the electromagnetic spectrum because all objects above a temperature of 0 K emit radiation falling within the IR range. Although a wide variety of techniques have been used to detect IR radiation, all these IR detectors can be

1 categorized as thermal or photon devices. Thermal detectors utilize temperature-dependent

properties of the detector material7, such as thermocouples and thermopiles which use the

thermoelectric effect. Bolometers and microbolometers8 are based on changes in resistance, Golay cells9,10 follow thermal expansion, and pyroelectric detectors11 utilize the temperature dependent spontaneous electric polarization that generates electric charges upon incidence IR irradiation

(known as pyroelectric effect).

Photon detectors have much higher sensitivity and faster response-time compared to thermal detectors7. These utilize electronic excitations in a semiconductor upon IR illumination as the basis of the detection method. The excited carriers can be measured as an electric potential or current change in the external circuit. Photon detectors can be divided into two types: photovoltaic and photoconductive. Photovoltaic-type detectors generate a photocurrent upon illumination, and they are usually constitute of p-n or p-i-n type semiconductor junctions, where p, i, and n denotes the p-

doped, intrinsic, and n-doped semiconductors, respectively. In photoconductive detectors, changes

in the conductivity (or resistivity) are monitored upon illumination. Typically, this requires an

external bias voltage and a load resistor to convert conductivity changes into voltage changes

which are easily measurable.

Initial photoconductive IR detectors were developed utilizing the band-to-band transitions or

dopant-to-band transitions. The band-to-band detectors typically require semiconductors whose

band edge is close to the energy of the photon to be detected. For sensing the IR region of the

spectrum, such detectors are typically fabricated of materials, which have difficulties associated

with material quality. HgCdTe and InSb are interesting materials which have been extensively

studied12 as photoconductive as well as photovoltaic systems. Cryogenically cooled HgCdTe has a

2 broad response range from 1 µm to 20 µm and InSb responds up to 5.5 µm at the same

temperature. Research is in progress to achieve uncooled HgCdTe detectors13. Extended InGaAs p-

i-n photodiodes responding up to 2.6 µm are commercially available. On the other hand, dopant-to-

band detectors operate at very low temperatures. In order to overcome the limitations of those two

methods intersub-band transition based detectors14,15 were introduced about two decades ago.

Quantum well detectors utilize intersub-band transitions, but are restricted to the absorption of normal incident radiation due to the selection rules16. Hence, these detectors require 45° coupling

or a corrugated surface (for grating coupling). Furthermore, quantum efficiency is greatly reduced

due to the selection rule permitting only one polarization mode of the incident light. Subsequently homo17 and hetero18 junction interfacial workfunction internal photoemission (HIWIP/ HEIWIP)

detectors were introduced. These utilize intra-band transitions (light-hole to heavy-hole transitions)

and are free of selection rule limitations. Since the free carrier absorption is proportional to the square of the wavelength19, the detector response is superior at longer wavelengths.

Uncooled detection of IR radiation is becoming important owing to the necessity of such detectors in a wide range of applications in the civilian, industrial, medical, astronomical, and military sectors. Cryogenic cooling or high-power-consuming multi-stage thermo-electric coolers (TECs) are not practical for most applications. This research study focused on novel concepts that can be used to develop uncooled IR detectors. Several successful novel concepts (including a pending patent20) with experimentally verified results have been already published in peer-reviewed

journals21-28.

In addition to uncooled detector development, this study investigated a GaSb homojunction based

terahertz (wavelength range from 30 µm to 1 mm) detector. The use of terahertz radiation as a tool

3 for characterization of materials has been widely demonstrated29. Applications can be found in various fields such as medicine30, industry, security, astronomy, and atmospheric studies. Some examples include cancer/tumor detection, non-destructive testing, toxic chemical detection, and gas sensing31. The key advantage of terahertz radiation in these areas is the ability to penetrate and distinguish between different non-metallic materials. This dissertation is arranged into five chapters and, the first chapter gives an introduction by describing the background and purpose of the study as well as the outline of the dissertation.

In the first part of Chapter 2, dye-sensitized near-IR room-temperature photovoltaic photon

detectors are presented. Dye molecules bonded to a semiconductor surface can inject carriers to a

conduction band by photo-excitation. This process known as dye-sensitization is used for extending the sensitivity of silver halide emulsions32 and was discovered a long time ago in 1839.

More recently (around 1991), dye-sensitization has been adopted to devise solar cells33. A near IR sensitive heterojunction n-TiO2/Dye/p-CuSCN (where Dye denotes a near-IR absorbing pigment) is developed21 to examine the possibility of using dye-sensitization for IR detection. Although the

responsivity is low and response slow compared to silicon photo detectors, dye-sensitized (DS)

detectors would be cost effective, especially for large area devices. They can operate at room

temperature and have the advantage of insensitivity to noise induced by band-gap excitations

(providing high specific detectivity of ~1011). Furthermore, the spectral response can be adjusted in the NIR range by choosing the appropriate dye. These results were published in Applied Physics

Letters.21

The second part of chapter 2 describes 1/f noise studies on nanostructured semiconductors, DS

photon detectors, and solar cells. In general, electronic devices are plagued with 1/f noise

4 originating from many causes. The most important factors contributing to 1/f noise in a

semiconductor is believed to be generation recombination of carriers and their trapping at defects

and impurity sites. Adsorption of moisture and electron acceptor molecules enhances the intensity

of 1/f noise. Amazingly, some molecular species that strongly chelate to the semiconductor surface suppress 1/f noise owing to passivation of the recombination sites. Thus, in addition to sensitization, the dye adsorbed on the nanocrystallites plays a key role in mitigation of recombinations. For this reason DS heterojunctions could also find application as low noise NIR photon detectors. Experiments conducted with oxide semiconductors (TiO2, ZnO, SnO2) indicate that the mode of binding of dyes at specific sites determines the extent to which the recombination and 1/f noise is suppressed. The transport of electrons in a nanocrystalline matrix is diffusive with a diffusion coefficient D depending on the trapping and detrapping processes. Thus, passivation of trapping sites by the adsorbed dye is expected to increase the response time which can be expressed as τ ~ L2/D, where L = thickness of the nanocrystalline film. These results were reported in Semiconductor Science and Technology.28 and Infrared Physics & Technology.27

Chapter 3 describes a colloidal quantum dot (CQD) based capacitive-type detector. It is shown that the high electronic polarizability of quantum dots can be utilized to devise photon detectors by embedding quantum dots in a dielectric media to form capacitors. Modulated light generates displacement currents and an expression is obtained for responsivity in terms of the properties of the quantum dot, the dielectric, and the detector geometry. A model detector consisting of PbS quantum dots embedded in paraffin wax is devised to illustrate the principle, giving ~0.6 A/W as an upper limit for the responsivity. As these systems sense only the variations of the light intensity, they could be operated at ambient temperature. This was published in Applied Physics Letters.25

5 Chapter 4 describes spin split-off transition based uncooled IR photon detectors. In the first part of

this study, heterojunction interfacial workfunction internal photoemission (HEIWIP) detectors that

are not optimized for split-off transitions were used to demonstrate IR response originating from

hole transitions between light-/ heavy-hole bands and the split-off (spin-orbit) band. A

GaAs/AlGaAs heterojunction with a threshold wavelength of ~20 µm, shows an operating

temperature of 130 K for split-off response in the range 1.5 –5 µm with a peak D* of 1.1×105

Jones. Analysis suggests that practical devices with optimized parameters are capable of achieving room temperature operation with higher specific detectivity. In the second part of the study a set of three p-GaAs/AlxGa1-xAs multiple heterojunction detector structures with free carrier threshold wavelengths of 8, 6 and 4 µm were designed and tested to investigate the best parameters for the spilt-off band detectors. Uncooled and even above room temperature (330 K) satisfactory operation was achieved for the 4 µm free carrier threshold sample with peak responsivity of 0.29 mA/W at

2.5 µm at 300 K. In addition to the expected split-off response, long wavelength response up to 60

µm was observed in this split-off sample. The mechanisms that could generate this type of response are also discussed. These results were reported in two Applied Physics Letters22,24 and

Infrared Physics & Technology23 article.

In Chapter 5, a GaSb based homojunction interfacial workfunction internal photoemission THz

(far-IR, >30µm) detector is presented. Metal-organic vapor phase epitaxy grown p-GaSb/GaSb

samples show 9.7 A/W peak responsivity and a peak detectivity of 5.7×1011 Jones with effective

quantum efficiency of 33% at 36 µm and 4.9 K. The detector exhibits a 97 µm (~3 THz) free

carrier response threshold wavelength. Results indicate that p-GaSb HIWIP detectors are

promising candidates as a competitor for current THz detectors. GaSb is not a well developed

material system compared to GaAs, Si, or Ge. The GaSb homojunction detector was analyzed as

6 an initial study to test the quality of the material and processing. Even though this detector operated

at liquid He temperatures, a design with lower (~15 µm) free carrier threshold should cover 8 to 14

µm atmospheric window region operating at higher temperature (240 K) which can be achieved

with TEC. This was reported in Applied Physics Letters.26

Appendix A describes the basic detector characterization techniques such as I-V-T, C-V-T, noise, and spectral response measurements. The terms related to the detector characterization (such as specific detectivity, responsivity, noise equivalent power, etc.) and their standard definitions are included in this section.

Several software packages have been developed using Microsoft Visual Basic to automate the

detector characterization process and improve quality and efficiency of the measurements. All

these programs are incorporated into standard measurement setups in the Optoelectronic

Laboratory at GSU. Appendix B describes the main features of these programs and the source code

is included at the end of each subsection.

7 Chapter 2

Dye-sensitized near-infrared room-temperature

photovoltaic photon detectors and 1/f noise in

semiconductor nanostructures

2.1 DS photon detectors

The development of devices for sensing IR radiation continues to be an important area of

investigation because of the application potential in a diverse variety of devices34-38. Most widely used IR detectors depend on electron-hole generation in low bandgap semiconductor structures by incident radiation. These detectors exhibit good signal-to-noise performance and very fast response. However, in order to achieve this, the semiconductor components of the detector need cooling. Thermal generation of carriers in a low bandgap semiconductor, impurity and defect

mediated recombination or thermally activated intersubband transitions (i.e., in quantum well

detectors) are limitations of conventional semiconductor photon detectors. In dye-sensitization

(DSN), dye molecules anchored to a semiconductor surface inject carriers into a band leaving dye ions of opposite charge on the semiconductor surface39. The transfer of the charge on dye ions to a counter-electrode through a suitable medium (liquid33 or solid40,41) yields a photocurrent having a spectral response (action spectrum) that is commensurate with the optical absorption of the dye. An

8 energetic requirement for DS electron injection is the location of the excited energy level of the

dye molecule above the semiconductor conduction band edge. Similarly for hole injection, the

ground level of the dye molecule should have a position below the valence band edge. The

possibilities of using high bandgap semiconductors insensitive to background thermal noise and

the flexibility of spectral response by choice of the dye are advantages of DSN based photon

detectors. Furthermore, DSN produces only one type of carrier in the semiconductor volume,

therefore the DS photocurrent remains insensitive to recombination at the grain boundaries or

impurity sites39. These attractive features of DSN have been exploited to construct solar cells using nanocrystalline films of oxide semiconductors33,39-41. Dyes absorbing light in the NIR region of the spectrum are commercially available for use as photographic sensitizers or laser dyes. This investigation indicates that some of these dyes sensitize the heterojunctions of the configuration, n- type semiconductor/dye/p-type semiconductor. A new detector based on nanocrystalline TiO2

(bandgap = 3.1 eV) film as the dye coated n-type substrate and p-CuSCN (bandgap 3.6 eV) as the

hole collector is fabricated and tested. Results indicate that these systems could be used as wavelength tailorable, room-temperature, low cost, IR detectors.

2.1.1 DS IR detector fabrication

Nanocrystalline films of n-TiO2 were coated on fluorine doped conducting tin oxide (CTO) glass plates (1 × 2 cm2, sheet resistance = 15 ohm/square) by the method reported earlier42. Titanium

isopropoxide (5 ml) mixed with propan-1-ol (20 ml) + glacial acetic acid (5.5 ml) hydrolysed by gradual addition of water (5 ml) is grounded with Degussa P25 TiO2 powder (median particle size

~50 nm). The resulting paste was painted over cleaned CTO glass plates (NaOH + propan-2-ol,

followed by water) heated to 150ºC, sintered in air at 450ºC for 10 min.

Glass CuSCN CTO CTO TiO2

Dye Glass

Graphite Gold

10 After removing the loose crust of TiO2 on the surface, the process was repeated until a film of ~10

µm thickness is formed. Dyes used in this investigation were anionic dyes IR 783, and IR 820 and

cationic dyes IR 792, and IR 1040 purchased from Aldrich (numbers indicate the peak absorption

wavelength of dye solution in nm). The anionic dyes readily anchor to the TiO2 surface and were coated by immersing the TiO2 film in a solution of the dye in 90% ethanol. The cationic dyes not directly anchoring to the TiO2 surface were deposited by pre-adsorption of another molecular species, usually an anionic compound43. Thereafter, the film was rinsed with ethanol and immersed in a solution of the cationic dye. The anionic compounds used for this purpose were bromopyrogallol red (BPR) mercurochrome (MC) and IR820.

The heterojunction n-TiO2/Dye/p-CuSCN was fabricated by deposition of p-CuSCN on dyed surface from a solution of CuSCN in propyl sulfide42. The outer CuSCN surface was coated with graphite and a gold plated CTO glass plate pressed onto the graphite surface served as the back contact of the detector. A schematic diagram indicating the construction of the device is shown in

Figure 2.1. Photocurrent spectral responses of the cells were recorded using a monochromatic- light, chopper lock-in amplifier system. Light intensities were measured with a calibrated silicon diode. (See Appendix B.2 for experimental setup and details about the in-house data collection software program.)

2.1.2 Experimental results and discussion

Nanocrystalline TiO2 films prepared by the method described above have effective surface areas

40 200-300 times the geometrical area of the film . Although the dye covers the TiO2 surface at the monolayer level, the large roughness factor of the film increases the light absorption cross-section.

Vacuum -1 Energy (eV) CB -2

-3 S* -4 CB -5 VB S -6 0 -7 VB -8 TiO2 Dye CuSCN

Figure 2.2 An energy level diagram showing the band edge positions of n-TiO2, p-CuSCN and ground (So – positioned arbitrarily) and excited (S*) states of the dye.

12 A schematic energy level diagram showing the band edge positions of TiO2, CuSCN and ground

* (S0) and excited (S ) levels of the dye is presented in Figure 2.2. The photovoltaic effect of the heterojunction originates via the following charge transfer scheme. Excited dye molecules (Dye*)

inject electrons and holes to the conduction and valence bands (CB and VB) of n-TiO2 and p-

CuSCN respectively, i.e.,

hDyeDyeν +→*

* −+ (2.1) Dye→+ Dye e(CB-TiO2 ) + h (VB-CuSCN)

* The relative positioning of the ground (So) and excited (S ) levels of the dye and band edges of the

two semiconductors (as shown in Figure 2.2) energetically permit the above charge transfers. The

44 positions of the band edges of TiO2 and CuSCN are known and agree with the relative band

* offsets as shown in Figure 2.2. However, the positions of So and S on the absolute scale were not measured, which normally requires a cyclic voltammetric determination of the position of So with

respect to a standard redox couple45. The observation of sensitized photocurrents with IR 783, IR

820, IR 792 and IR 1040 shows that these dyes have ground and excited level positions satisfying the above conditions. The spectral responsivities of the detectors sensitized with IR dyes are shown in Figure 2.3. The red-shifts of the peak positions in action spectra are caused by bonding of dyes to the semiconductor surface. The responsivities at the peak absorption wavelengths summarized in

Table 2.1, are nearly two orders of magnitude smaller than that of silicon detectors46. The peak

* 10 specific detectivity D of the system n-TiO2/MC-IR792/p-CuSCN was found to be 9.5×10 cm Hz-1/2 W-1 at 812 nm. (noise characteristics measured using the low noise SR560 preamplifier and the SR785 fast Fourier transform Dynamic Signal Analyzer; see Appendix B.3.1 and A.4.1 for

experimental setup and calculation method)

3 IR820 CuCNS BPR IR820 CuCNS IR783 CuCNS HgCrom IR792 CuCNS 2 IR820 IR1040 CuCNS BPR IR1040 CuCNS

Responsivity (mA/W) 0 700 800 900 1000 1100 Wavelength (µm)

Figure 2.3 Spectral responsivity of the heterojunctions (a) n-TiO2/IR820/p-CuSCN (b) n- TiO2/BPR-IR820/p-CuSCN (c) n-TiO2/IR783/p-CuSCN (d) n-TiO2/MC-IR792/p-CuCSCN (e) n- TiO2/IR820-IR1040/p-CuSCN (f) n-TiO2/BPR-IR1040/p-CuSCN

14 Poor photon-to-photocurrent conversion efficiency could be a result of low probability of injection

of carriers by the excited dye molecule. Photophysical properties of the dye, the relative energetic

positions of ground and excited states with respect to the band edges, density of states in the bands

(i.e., electrons in the CB of TiO2 and holes in the VB of CuSCN) and mode of anchoring of the dye

molecule to the TiO2 surface determine the injection rate. When photocurrent transients of the detector sensitized with IR 792 were examined, the rise and fall time constants turned out to be of the order 5 and 3 ms, respectively. Clearly, the response is slower than that of conventional semiconductor detectors. This behavior of the device is a consequence of the slow diffusive transport of electrons in a film consisting of TiO2 nanocrystallites interconnected to each other by sintering. The response time τ of the detector can be expressed in the form,

L2 τ ≈ (2.2) D where L = film thickness, D = diffusion coefficient (which depends on film morphology and

intrinsic material properties of the two semiconductors). Thus, the response time happens to be

highly sensitive to the film thickness, i.e., a reduction in film thickness leads to faster response.

However, the responsivity of the detector determined by the light absorption cross-section of the

dye coated nanocrystalline film varies linearly with the film thickness. Optimization would be

possible to meet the requirements of specific practical applications.

2.1.3 Conclusion and future possibilities

This investigation demonstrates that dye–sensitization of high bandgap semiconductors can be

utilized to devise NIR detectors. They have the advantage of not being sensitive to thermal noise

and radiation that initiate bandgap excitations.

Table 2.1 Responsivities (R) of the detectors at peak absorption wavelengths (λmax) of different sensitizers.

Dye λmax (nm) R (mA/W)

IR820 866 0.3

BPR-IR820 876 1.1

IR783 808 0.4

MC-IR792 812 2.7

IR820-IR1040 858 1.0

BPR-IR1040 1056 0.3

16 As expected, the specific detectivities of DS detectors are found to be quite high despite low

* responsivity. The specific detectivity D of the system n-TiO2/MC-IR792/p-CuSCN was found to

be 9.5×1010 cm Hz-1/2 W-1 at 812 nm. As shown in Figure 2.4, the variation of the dark current

noise spectral density S(f) with frequency at room-temperature (292 K) is low and largely

frequency independent beyond a frequency of ~1 kHz. High bandgap semiconductors remain less

susceptible to stochastic intermittency of thermal excitations that contribute to 1/f noise47,48. The peak spectral response of these devices can be readily adjusted by choice of the dye and tuning by structural modifications to the dye molecule. DS NIR detectors would be very cost effective devices because they are based on polycrystalline semiconductor materials and the processing does not involve vacuum technology. Instead of CTO glass, TiO2 film could be deposited on a flexible plastic substrate49. This will allow detector to be fabricated even on a curved-surface. DS NIR detectors can be extended to panchromatic detection utilizing dye-multilayer structure44 or pair of

cationic and anionic dyes50,51 since this idea is already demonstrated on DS solar cells. However, in the present form the responsivities are of the order 10-3 A/W (Table 2.1), i.e., two orders of

magnitude smaller than familiar semiconductor detectors. Extensive effort is underway for

improvement of the efficiencies of DS solar cells. The outcome of these investigations could pave

the way for the development of highly sensitive DS IR photon detectors. Combination of IR dyes with visible sensitizers may also enhance the efficiencies of DS solar cells. In fact, the heterojunctions that incorporate BPR or MC in addition to the IR dye are also sensitive to the visible spectrum.

101E-25-25 Detector Structure

TiO2/MC-IR792/p-CuSCN at room temperature /Hz) /Hz) 2 2 -27 101E-27 (f) (A (f) (A I I S S

-29 101E-29 04812 f (kHz)

Figure 2.4 Power spectral density of the dark current noise of the hetrojunction n-TiO2/MC- IR792/p-CuSCN.

18 2.2 1/f noise in DS photon detectors and photovoltaic cells

2.2.1 Introduction

The lowest possible level of noise provides the highest detectivity of the photon detectors.

Therefore, it is very important to understand the cause of noise and techniques of its suppression.

Dye-sensitized near infrared photon detectors (DSNIRPDs) described in Chapter 2 and DS solar

cells (DSSCs) based on nanocrystalline high bandgap oxide semiconductors receive much

attention as cost effective alternatives to the conventional photon detectors and solar cells made

from low bandgap semiconductors. The functioning of these devices depends on DSN, i.e., a

process by which a photo-excited dye molecule anchored to a semiconductor surface injects an

electron to the conduction band forming a dye cation33,52. The positive charge on the dye cation can be transferred to a suitable hole collecting medium in contact with the dyed nanocrystalline surface to form heterojunction of the configuration n/Dye/p , where n denote the nanocrystalline n-type

semiconductor, and p denote hole collecting medium. In one version of DSSCs, the hole-

collecting medium is a redox electrolyte33,52 (also known as Gratzel type solar cells (GDSSCs)) which efficiently collects the positive charge on the dye cations formed during electron injection, whereas in the other version p is a hole collecting solid material40,53 (i.e., a p-type semiconductor of

appropriate band positions). The electron injected into the n-type material and the dye cation on its

surface undergoes recombination. However, the rate of recombination happens to be several orders

of magnitude slower than the rate of injection and this is one of the reasons why the DSNIRPDs

and DSSCs function, converting light to electricity, at reasonably high quantum efficiencies52. The

dye coverage on the semiconductor surface needs to be maintained at the monolayer level to avoid

insulation by thick dye layers and to prevent rapid quenching of the excited molecules by mutual

interaction. Although the dye coverage is at the monolayer level, the large roughness factor (~

19 1000) of the oxide semiconductor greatly increases the light absorption cross-section. As DSN

involves carrier transfer to one band, bulk recombinations are absent, but the large effective area of

the interface makes DSNIRPDs and DSSC susceptible to surface recombination. However, DSSCs

deliver quantum efficiencies exceeding 85% and energy conversion efficiencies around 10% are

readily achievable33,52, indicating that recombination does not occur at the expected rate. Trapping

and detrapping of carriers at the surface of semiconductors generate 1/f noise54,55. The interactions of carriers with both bulk and surface trap sites contribute to 1/f noise. In nanocrystalline semiconductors where the surface to bulk ratio is exceptionally large, the trapping-detrapping of carriers at surface states makes the most significant contribution to 1/f noise. A nanocrystalline surface is heavily populated with defects and adsorbed species that act as trapping and recombination sites. This chapter describes the observations of 1/f noise in bare and dye coated nanocrystalline films of TiO2. It is found that in bare nanocrystalline TiO2 films, adsorbed

molecular species that produce electron acceptor surface states (e.g., water vapor, iodine) induce

1/f noise. However, in dye coated TiO2 films, the passivation of active sites on the TiO2 surface by the dye suppresses the generation of 1/f noise.

2.2.2 Frequency dependent noise

The electric current through a conductor at a constant bias voltage and temperature undergoes

fluctuations around a mean.54-58 In addition to the frequency (f) independent thermal and shot noises, conducting materials and electrical devices also display a noise whose spectral power density exhibits a 1/f  dependence54-58 (more generally a 1/f δ variation where δ is a positive index,

generally close to unity). Under thermostatic conditions the current passing through a

nanocrystalline semiconductor films exhibits 1/f noise according to Hooge’s formula59

20 2 AI0 S(f) = (2.3) f δ where Io= mean value of the fluctuating current I(t) = Io+ X(t) , with =0 and

2 ⎛⎞1 T Sf()= lim⎜⎟ Xte ()−2πift dt . (2.4) T →∞ ⎜⎟2T ∫ ⎝⎠−T

The constant A in (1) which measures the level of noise, generally takes the form59 A = ϒ/N, where

N = the total number of free charge carriers in the sample and the parameter ϒ is referred to as the

Hooge’s constant. Interaction of carriers with defects, surface states and associated events such as recombination and trapping-detrapping are believed to be the major causes of 1/f noise in semiconductors.54-60 Consequently, 1/f noise measurements receive considerable attention as a tool for characterization and understanding the nature of carrier relaxation processes in semiconductors.55,56 In electronic measuring devices, the lowest possible level of 1/f noise is desired to improve the detectivity. Also, a high 1/f noise level usually indicates an underlying dissipative process61. Both bulk54,55,60 and surface54,55,62 interactions of carriers contribute to 1/f noise in semiconductors. Because of the large surface to volume ratio, surface effects are expected to be a major cause of 1/f noise in nanocrystalline semiconductors. Furthermore, the slow charge transport in nanostructured materials has been attributed to trapping and detrapping of electrons in intraband-gap surface states.63-65

2.2.3 Sample preparation and experimental setup for noise

measurements

Nanocrystalline films used for measuring the noise in the electrical current were prepared as described below. A scribe (~ 8 µm thick) is drawn on the surface of a FTO glass plate (1.5 × 2 cm2,

Top View

Scribe CTO TiO2

Side View

Glass

22 sheet resistance 12 ohm cm-2) with a fine diamond point to break the electrical connectivity. A layer of colloidal TiO2 (thickness ~ 10 µm) was screen printed above the scribe and the plate is sintered at 430o C for 30 minutes to form the sample geometry66 represented in Figure 2.5. In some experiments, films were coated with BPR or cis-dithiocyanatobis (4-4’-dicarboxylic acid-2,

2’Ru[II]) (N3) by soaking them in alcohol solutions of these dyes (~2.5 × 10-3 M). The experimental setup used for the noise measurements is shown in Figure 2.6. The sample placed in a chamber with facilities for evacuation and heating was connected in series with a resistor R = 56 kΩ and an 18 V battery. A low noise preamplifier amplified the voltage fluctuation across the sample and a power spectrum analyzer (Stanford Research SR785 Fourier Transform Dynamic

Signal Analyzer) computed S(f) and plotted its variation with f.

2.2.4 Results and discussion

When the chamber is filled with air at atmospheric pressure and relative humidity (RH) 27% (23

°C), the noise power spectrum (i.e., plot of S(f) vs. f) clearly displayed frequency dependent noise

(FDN). On evacuation of the chamber, FDN persisted but at lower intensity. However, if the film is heated to ~90 °C during evacuation, FDN disappeared completely even after cooling the sample to room temperature under vacuum (10-6 Torr) and did not reappear when the chamber was filled with dry N2 or O2 (Figure 2.7 curve (a)). Generation of FDN resumed when water vapor was introduced into the chamber. The curve (b) of the Figure 2.7 shows the noise spectrum of the sample in a nitrogen atmosphere at RH ~70%. The above observations show that the factor which contributed to FDN when the sample was in air was also moisture. When the experiment was repeated replacing water with acetonitrile, FDN was not detected. FDN was once again observed with introduction of iodine into the chamber filled with N2 (Figure 2.7, curve (c)).

Sample Temp. N2, H2O(g) Sensor Heater PC Vacuum

FT Signal Analyzer (SR785) R

Low Noise Pre- Amplifier (SR560)

24 It was interesting to note the difference in behavior of bare and dye coated TiO2 films. Here, iodine was ineffective in creating FDN and the noise power density (f independent) remained unaltered in the presence of iodine vapor in the chamber (Figure 2.7 curves (d), (e), (f), (g)). Again the influence of moisture in generating FDN is less in dye coated TiO2 films as measured noise levels here are smaller compared to that of the bare TiO2 films. Table 2.2 gives the values of the parameters A, δ and ϒ when the noise spectra of different systems are fit with the formula (2.3).

The magnitude of the parameter A for a sample of given geometry (i.e., film thickness, length and breadth of the scribe) measures the level of 1/f noise. In the absence of FDN, the background noise

(Figure 2.7 curves (a), (d) and (e)) originates from thermal and environmental influences and does not follow formula (2.3). Nevertheless, for comparison Table 2.2 gives the values of A and ϒ for the frequency independent situations as well, setting δ = 0 in formula (2.3). Hooge’s constant ϒ is

67 17 -3 estimated using the literature value for carrier density of TiO2 (∼1×10 cm ) and volume of TiO2

-3 3 in the scribe = 7.2×10 cm (estimated from the knowledge of the volume of TiO2 in a large size film). The above experiments indicate that the electron acceptor states produced by adsorbed species generate 1/f noise in nanocrystalline TiO2 films. Water is known to dissociatively adsorb

68 on the TiO2 surface forming H and OH fragments . The acceptor OH radicals act as electron trapping sites. Similarly, iodine adsorbed on the TiO2 surface could also trap electrons. Trapping and detrapping of electrons at the surface states is known to be a cause of 1/f noise in semiconductor materials.54 This process becomes exceedingly important for nanostructured films because of their large surface to volume ratio. In a dyed TiO2 film, water and iodine absorption sites get passivated by surface chelation of the dye molecules and therefore 1/f noise is suppressed.

10-16 (c)

(b) (i) 10-19 (h)

-22

S(f) (A²/Hz) S(f) 10

(a) (d) (e) (f) (g) (j) (k) (l) 10-25 100 1000 10000 f (Hz)

Table 2.2 The values of parameters A, δ and γ for different systems obtained by fitting noise data -4 with formula (2.3), biasing voltage = 18 V, and Io = 3.2×10 A.

sample δ Α ϒ

-18 -7 ΤiO2 (vacuum) 0 4.4×10 3.2×10

-18 -7 TiO2 (N2) 0 4.4×10 3.2×10

-18 -7 TiO2/BPR (vacuum) 0 4.4×10 3.2×10

-18 -7 TiO2/N3 (vacuum) 0 4.4×10 3.2×10

-18 -7 TiO2/BPR (N2) 0 4.4×10 3.2×10

-18 -7 TiO2/N3 (N2) 0 4.4×10 3.2×10

-10 1 TiO2 (N2 ,RH = 70%) 1.25 8.8×10 6.3×10

-11 0 TiO2/BPR (N2, RH= 70%) 1.15 4.4×10 3.2×10

-10 1 TiO2/N3 (N2, RH = 70%) 1.30 5.7×10 4.1×10

-9 2 TiO2 (N2, saturated I2 vapor) 1.37 5.8×10 4.2×10

-18 -7 TiO2/BPR (N2, saturated I2 vapor) 0 4.3×10 3.1×10

-18 -7 TiO2/N3 (N2, saturated I2 vapor) 0 4.4×10 3.2×10

27 When the RH in the chamber is high (≥40%), dye bonded to TiO2 surface seems to desorb partly, allowing water adsorption. This explains the observation that in an environment of high H2O vapor pressure, dyed TiO2 films also exhibit 1/f noise.

2.2.5 Conclusion

The observations presented above have profound implications for the performance of GDSSCs33 and DSNIRPDs21. In fact they explain why the GDSSCs and DSNIRPDs work so well. Although the substrate through which the electrons move is highly populated with defects, the adsorbed dye passivates these surface recombination centers. As the trapping-detrapping process at surface states is relieved by dye chelation, the dye absorption also facilitates transport of electrons across the nanocrystalline matrix. In fact, it has been noted that the diffusion coefficient of electrons in dyed nanocrystalline films is higher than that of bare films.69 If there are voids in the dye monolayer on

TiO2 surface, interaction of iodine at the points of exposure of TiO2 would be detrimental to the functioning of the GDSSCs. The trapping of electrons by iodine adsorbed at the voids in the dye layer will cause recombination. Partial desorption of the dye, followed by iodine adsorption seems to be a major cause of recombination loss in the GDSSCs. It is interesting to note that successful attempts have been made to synthesize dyes that resist desorption to the electrolyte.70 Our experiments also indicate the importance of hydrophobic52 and water free electrolytes. Noise measurement also offers a way of characterizing dye adsorbed nanostructured semiconductor films. The dyes used in this study, N3 and BPR, strongly complex onto the TiO2 surface via carboxylate and hydroxyl ligands respectively, eliminating the surface hydroxyl groups.71 The 1/f noise studies would be of value in understanding other modes of interactions of molecules with nanocrystalline semiconductor materials.

28 Chapter 3

Displacement currents in colloidal quantum dots embedded dielectric media: A method for room temperature photon detection

3.1 Introduction

The unique properties of low dimensional semiconductors offer opportunities for application in almost all areas of electronics72-76. Many concepts have been extensively studied identifying potential applications. Quantum dots (QDs) are used in photon detection72-74,77, especially the near infrared (NIR) and infrared (IR) regions of the spectrum78-81. Utilizing size quantized band–gap modulation, QDs of low effective carrier mass semiconductors can be sensitized to the electromagnetic spectrum from ultraviolet (UV) to far IR. Photovoltaic and photoconductive detectors have been made from QDs blended in conducting polymers82-84. In photovoltaic detectors, interpenetrating networks of polymer and QDs communicate with two electrodes. The excitons generated by the incident photons decompose at the interface into electron-hole pairs which separate into the two regions generating a photocurrent and a photovoltage. Photoconductive type operates by derivation of a current by an external voltage via movement of carriers across the polymer medium. Properties of individual QDs are greatly obscured by clustering and aggregation,

29 and also obtaining electronic contacts to QDs would not be an easy task. The photoconductive detectors, where the QDs are homogeneously impregnated into a solid substrate avoid the above problem. This study shows that by embedding QDs in a film of high dielectric material to form a capacitor, the displacement current generated by modulated light can be used as a signal to detect photons. As in pyroelectric detectors85, this technique has the advantage that only the intensity modulated light generates signals enabling room temperature operation for sensing IR radiation.

Again as in photoconductive QD-polymer detectors, their fabrication does not require electrical connections to the QDs. A capacitor with PbS colloidal quantum dots (CQDs, Colloidal Quantum

Dots are synthesized from precursor compounds dissolved in solutions) embedded in paraffin wax

(Figure 3.1 a) was used to illustrate the principle.

3.2 PbS colloidal quantum dot (CQD) preparation and detector

fabrication

PbS CQDs embedded paraffin wax films were prepared by the following method. Water insoluble lead oleate was synthesized by mixing equal volumes of lead acetate (0.1 M) and sodium oleate

(0.2 M) solutions. The white precipitate of lead oleate was separated, washed with water and dried in a vacuum. A weighed amount of lead oleate was dissolved in molten purified paraffin wax

(melting point ~ 64º C, dielectric constant = 2.4) and a thin layer of wax was spread on the surface

2 of a conducting glass plate (1.5×1 cm ). After solidification of wax, the plate was inserted into a N2 atmosphere containing H2S (~ 20% by volume) and propan-2-ol vapor and left there for 2 hrs. H2S diffuses into the wax impregnating it with oleic acid capped PbS CQDs. Presence of the vapor of a slightly polar liquid (propan -2-ol) facilitates this diffusion controlled reaction. The absorption spectrum of the film is shown in Figure 3.1 (b) and the spectrum of the film material dissolved in

30 hexane was also recorded. These spectra suggest a polydispersion of PbS CQDs in wax with a median diameter of ~ 8 nm. To form the capacitor, the plate is warmed to melt the wax and another conducting glass plate posed above to cover an area of 1 cm2 and fill the capillary space with molten wax. When the wax solidifies, the plates hold together and leads are connected to the two protruding ends of the conducting glass plates (see Figure 3.1 (a)). The measured capacitance (200 pF) of the system was nearly of the same order as that of a capacitor of same dimensions (area = 1 cm2, thickness = 10 µm) with a film of pure wax and the resistance exceeded 1 GΩ.

3.3 Detection mechanism, results, and discussion

Calculations indicate that QDs have several orders of magnitude larger polarizabilities than that of atoms and molecules86,87. This has been confirmed by quantum confined Stark effect88,89 and measurement of the electronic polarizability of optically generated excitons in quantum dots90.

Using effective medium theory90,91, the electric susceptibility χ of the QD- dielectric composite can be expressed as,

χ = εκα0n (3.1)

Where

9ε 2

κ = 2 (3.2) (2)εQD + ε and where n = number density of excitons per QD, α = exciton polarizability, ε = dielectric constant of the composite and εQD = dielectric constant of the QD material. Hence, if a capacitor of thickness s consisting of N QDs of given size per unit volume is placed in a constant electric field

E, the displacement current density dD/dt = J(t) originating from time variation of n can be written as,

1.6 (a)

1.2 s Conducting Tin Oxide Glass 0.8 (b) Paraffin wax PbS quantum dots Absorbance Absorbance

0.4

0 400 500 600 700 800 900 Wavelength (nm)

32 dD dn Jt()== sNεκα E . (3.3) dt0 dt

For simplicity, the displacement current response of the system was analyzed by assuming that the photon flux incident on the capacitor modulates as, I = I0 (1+sinωt). Thus the rate of exciton generation is given by,

dn =+φωIsintkn(1 ( )) − (3.4) dt 0 where φ is the quantum efficiency of exciton formation and k is the exciton recombination rate constant. Solving Eq.(3.4) for n and combining with Eq.(3.3), the displacement current density can be expressed in the form,

φωκαεNEI ⎛⎞ke−kt Jt()=++00⎜⎟ sin (ωδ t ) (3.5) ωω22++kk⎝⎠ 22 where tan δ = k/ω and the initial condition is J(0) = 0, t = 0. When the transient in Eq. (3.5)

decays, the detector output current density simplifies to

φNEI00καε ω sin() ω t + δ Jt()= . (3.6) ω 22+ k Setting E = V/s (V = applied voltage bias), the current (A/W) and voltage (V/W) responsivities of the detector can be obtained as follows (RL, Rd as indicated in Figure 3.2).

2()φ νωVN καε0 2()φν ωVN καε0 RLd× R R = RV =×. (3.7) 22 22 hsνω+ k hsνω+ k RRLd+

The circuit used for the measurement of the photoresponse, including the equivalent circuit of the detector is shown in Figure 3.2. The effect of the parasitic capacitance in the circuit is not very

1/2 strong at low chopping frequencies (i.e., ω < [RdCd] ). The plot of responsitivity vs. wavelength

33 at different bias voltages (8.7 V to 40 V) and a fixed chopping frequency of 57 Hz is shown in

Figure 3.3. Despite the simplicity of the system, the response extends from 400 - 1100 nm.

The formula (3.7) enables calculation of the intrinsic responsivity of the detector in terms of the properties of the QDs, the embedding dielectric medium, the thickness of the film and the bias voltage. Responsivity depends on several factors, i.e., size and the number density of QDs, their polarizability, the thickness of the capacitor and the applied bias. The response increases linearly with the applied bias according to Eq. (3.6) up to ~ 20 V and deviation from linearity is seen thereafter. A higher bias will also increase the noise and at biasing values exceeding the field ionization threshold, the motion of dissociated electrons and holes will also contribute to the displacement current, causing a deviation from the linear variation. The Eq. (3.7) involves the recombination rate constant k which is sensitive to the structure of the dot (i.e., capping, size and shape) and its environment. Under optimum conditions (i.e., absence of trapping of the carriers) the exciton recombination is slow (~ ms range) and the condition ω>> k should be satisfied. The constant k can be readily estimated from photocurrent transients (when radiation of constant

-ikt intensity is interrupted, the transient signal takes the form sNκαΕφIoe ) and the value obtained is of the same order of magnitude (i.e., ms). For optimization of the responsivity, the quantum dots need to be densely packed keeping the film thickness s comparable to the mean free path of photons. However, in general conductor-insulator composites exhibit percolation thresholds92 when the packing fraction of the conducting material exceeds a critical value N=NC. In the present system such a threshold would depend on the size of the quantum dots. However, determination of this threshold for monodispersions of PbS CQDs in paraffin was not succeeded.

To Pre- J(t) Amplifier Rd Cd

Detector

Figure 3.2 The equivalent circuit of the detector (inside the dashed box) and the circuit used for measurement of the photoresponse (Cd = detector capacitance, Rd = detector resistance).

200 300 K 8.7 V 20 V 30 V 150 40 V

100

50 Responsivity (V/W) 0 400 600 800 1000 Wavelength (nm)

Figure 3.3 The responsivity of the detector under different bias voltages. (85 MΩ resistor was used as Load resistor RL and chopping frequency was 57 Hz).

36 When the total amount of PbS incorporated into the wax reached ~15 % by weight, PbS begins aggregating masking the detection of this effect. Almost complete absorption of incident radiation avoiding any percolation threshold would be possible by increasing the film thickness. In general, near percolation thresholds, systems tend to be noisy92 and therefore optimization should be achieved keeping N well below NC and appropriate adjustment of s. In the present investigation no attempt was made to optimize the system. In the measurement reported, the bias voltage was varied from 1 to 40V with an 85 MΩ load resistor (RL). The plot of voltage responsivity vs. the wavelength of the incident radiation is shown in Figure 3.3 and the responsitivity at the peak absorption (λ = 540 nm ) was found to be 195 V/W at a bias of 40V and the specific detectivity under the same condition was determined as 3×108 cm Hz1/2/W.

3.4 Conclusion

The reported detectors based on displacement current of the CQD embedded dielectric media have the advantage of only detecting the change in the light intensity so that they are not saturated by the background at 300 K, while the inherent high resistance in the capacitor approach eliminates the dark current problems present in most room temperature detectors. The responsivity of the present system can be compared to that of a photoconductive detector of the same bulk material as follows.

As the photoconductive current density is Jc = enµΕ (µ = eτ / m), µ = mobility,τ = scattering time, m = carrier effective mass and taking low frequency molecular exciton polarizability =

2 e JsNAω −5 2 ( ωο = exciton binding energy / h ), we can be obtain =2 ∼ 10 (Α = detector ε00mω JC τω0 area = 1 cm2, ω = 57 Hz, N = 107 and exciton binding energy = 10 meV ). Due to the less than ideal coverage of CQDs in the dielectric (i.e., N = 107) the responsivity is very low compared to a

37 photoconductive detector. Owing to its low melting point and brittleness, paraffin wax is not the best material to embed CQDs. However, due to the simplicity of the preparation, paraffin wax was selected as the dielectric; any other dielectric material including silica, glass or polymers could also be used. Better methods of preparation of PbS CQDs and use of other embedding dielectrics should improve the performance, when N is increased by several orders of magnitude. It is straightforward to extend the concept proposed here to QDs of other materials and nanowires.

Carbon nanotubes which possess high polarizabilities93 with band gap taliorability would provide an option to fabricate multiband detectors. Thus more versatile photon detectors may be developed if nanotubes are used instead of quantum dots. An additional merit is the sensitivity to polarized radiation if the nanotubes are aligned in the dielectric medium. Furthermore, large aligning torques can be applied to carbon nanotubes, in a highly resistive dielectric medium compared to a conducting medium. The effects of multi-exciton production will also be reminiscent in these detectors, especially if PbS is replaced by PbSe; In PbSe-conducting polymer photon detectors, enhancements in quantum efficiency originating from impact ionization has been observed94.

The optimization of the detectors based on this technique requires further studies on quantum dot/ nanotube impregnated dielectric media and assessment of noise and ways minimizing it. It is also important to test the room temperature operability using CQDs that absorb longer wavelengths.

Displacement current measurements in CQD embedded dielectric media could also give useful information on properties of low dimensional semiconductors.

38 Chapter 4

Split-off transition based uncooled infrared detectors for 3-5 µm and beyond

4.1 Introduction

Uncooled infrared detectors have attracted much attention recently due to their numerous applications in data communication, fire fighting, electrical circuit trouble shooting, surveillance, bio-molecular identification and the fields of astronomy and defense. Avoiding cryogenics for detector cooling can reduce the cost and weight: simplifying the sensor systems and allowing for widespread usage. One of the major drawbacks of infrared photon detectors is the need for cooling far below room temperature in order to suppress the thermal generation processes. These thermally generated carriers (dark current) effectively reduce the signal to noise ratio of the detector. The cooling requirements introduce difficulties for low cost, compact lightweight, and logistics for most infrared systems. Numerous studies have been conducted over the years to find new material systems and architectures for uncooled IR photon detection95,96. An important intrinsic semiconductor material for uncooled infrared photodetector applications95 has been HgCdTe, which recently showed97 200 K operation. Narrow bandwidth quantum well98 and quantum dot based detectors99 working at room temperatures have also been reported. Extended InGaAs p-i-n

39 photodiodes responding up to 2.6 µm in ambient conditions are commercially available. One of the drawbacks associated with HgCdTe detectors is the lack of possibilities for optimization because of the problems caused by lattice, surface, and interface instabilities. These problems originate from weak bonding characteristics of II–VI semiconductors and from high Hg vapour pressure.

Weak bonding reduces the strength of the material, resulting in poor mechanical properties and creating difficulties in material processing. Moreover high Hg vapour pressure makes the composition control over a large area difficult, causing serious problems for the focal plane array applications. This has intensified the search for alternative infrared material systems. As a well developed material system GaAs is free of most of the above problems.

Highly p-doped GaAs exhibits enhanced absorption around 2- 4 µm range, beyond the free carrier absorption, due to light hole (L-H) / heavy hole (H-H) to split-off band transitions. The split-off band effects have been experimentally observed in the emission of GaAs metal semiconductor field effect transistors100 and have enhanced the response of GaInAsP101 quantum wells and

GaAs102 quantum wells. Extensive theoretical studies on the importance of the spin split-off band and the tunnelling properties of the holes through AlxGa1-xAs/GaAs heterostructures are reported

103 + elsewhere . This study was based on two sets of p -GaAs/AlxGa1-xAs heterostructure detectors.

The first split-off response was observed in a HEIWIP structure designed for the detection of MIR radiation. The second set of samples was designed to study the effects of the free carrier threshold wavelength on the split-off response.

40 4.2 Heterojunction Interfacial Workfunction Internal Photoemission

(HEIWIP) detectors

The active region of the basic HEIWIP detector consists of one or more periods, each consisting of a doped emitter and an undoped barrier layer. These multiple emitter/barrier layers are sandwiched between two highly doped contact layers as shown in Figure 4.1(a). Depending on the doping required for ohmic contacts, the top contact may also serve as the top emitter layer. A p-type band diagram for a single period of a detector is shown in Figure 4.1(b). Here, the workfunction (∆) is given by ∆ = ∆d + ∆x where ∆d and ∆x are the contributions from doping and the Al fraction, respectively104. The dashed lines indicate the valence-band edge if the barriers were GaAs. As the

105,106 Al fraction is reduced, ∆ will be limited by ∆d, which in turn is a homojunction detector . The detection mechanism can be divided into three main processes; i) the photoabsorption which generates excited carriers, ii) escape of the carriers, and iii) collection of the escaped carriers. Free carrier absorption in the emitter layers initiates the process. The excited carriers then escape from the emitter layer by internal photoemission at the interface between the emitters and barriers. The applied electric field will sweep the carriers out of the active region. This standard mechanism can also occur for electrons in the conduction band of n-type detectors. By having a high enough doping to have the scattering length similar to the emitter thickness, the carriers will scatter before the wave function can interfere with itself and hence will not form discrete quantum states inside the well. This makes the carrier distribution in the emitter three dimensional but still bound. The

HEIWIP detectors designed for the MIR and FIR ranges also showed response peaks at NIR region22. These peaks, which matched the GaAs split-off, were superimposed on the free carrier response.

(a) Top Contact p++ GaAs

N periods

GaAs Emitter AlGaAs Barrier Bottom Contact p++ GaAs

Substrate

(b)

Figure 4.1 (a) Typical structure of a GaAs emitter AlGaAs barrier HEIWIP detector. (b) Band diagram showing the workfunction (∆) for photoemission of carriers. Here, ∆ is given by ∆ = ∆d + ∆x where ∆d and ∆x are the contributions from the doping and the Al fraction, respectively. The dashed lines indicate the valence-band edge if the barriers were GaAs.

42 4.3 Split-off band detector mechanism

A split-off detector has a similar structure as HEIWIPs, described in Section 4.2. The emitters must be p-doped since the transitions involve are intra-valence band. A band diagram (E-k) for an emitter region of the detector is shown in Figure 4.2. In order to explain the detection mechanism, three valence bands will have to be considered as shown in Figure 4.2 , the L-H and H-H bands which are degenerate at k = 0, and the split-off band which is separated from them by an energy

EE-SO. Under equilibrium conditions, a p-doped region will have a Fermi level in the L-H and H-H bands, but above the split-off band maximum. The arrows in the Figure 4.2 indicate the possible threshold transition mechanisms. These transitions could be direct or indirect. Once the carrier is in the split-off band, it can escape directly or scatter back into the L-H/H-H bands and then escape.

For a direct transition (shown by arrow 1 solid part) there is no phonon involved so k is conserved.

The excited carrier then must scatter back to the L-H band (or possibly the H-H band although this involves much higher k changes) in order to escape. This phonon involved scattering is shown by the dashed arrow. The threshold for this process is determined by the difference of energy in the light and split-off hole bands at k corresponding to the Fermi energy shown by EF in the Figure 4.2.

For the indirect transition (shown by arrow 2) a phonon is involved and higher energies are possible. The high energy transition which is below the barrier in the split-off band could escape directly (it is not shown as this is a purely spatial change and does not affect the k-space picture).

The indirect absorption has two thresholds. For escape with a scattering it is the difference of the

Fermi energy and the split-off band at k=0 in the emitter (∆E-SO). For escape without scattering, it is the difference between the Fermi energy and the split-off band at k=0 in the

E ∆ = E -E CB L/H B-L/H F ∆SO = EB-SO-EF

∆E-SO= EE-SO-EF k EF E H-H (2) (1) B-L/H Band L-H Band EE-SO

EB-SO

SO Band

Figure 4.2 A band diagram for an emitter region of the detector, illustrating the different IR detection threshold mechanisms. The horizontal dashed lines EB-L/H and EB-SO indicate the L- H/H-H and split-off band maximum (k=0) positions in the barrier. The horizontal dotted lines EF and EE-SO indicate the Fermi energy and the split-off energy in the emitter at k=0. The arrows indicate the possible threshold transition mechanisms (1) direct transition from L-H band to SO band followed by scatter back to L-H band (2) indirect transition followed by scatter back to L-H band.

44 barrier (∆SO). The horizontal dashed lines EB-L/H and EB-SO indicate the L-H/H-H and split-off band maximum (at k=0) level in the AlxGa1-xAs barrier. The horizontal dotted lines EF and EE-SO indicate the Fermi energy and the split-off energy at k=0. Even though ∆SO is constant for a given material system, ∆L/H (also known as free carrier threshold) can be adjusted by varying Al fraction

18 x and the doping concentration of the emitter layer . The ∆L/H is the lowest barrier for the excited carriers in L-H /H-H bands which determine threshold wavelength for the free carrier mechanism and also major contribution for dark current hence determined maximum operating temperature.

By making ∆L/H larger it is possible to make split-off transitions as dominant detection mechanism and increase operating temperature. However, higher ∆L/H can lead to lowering the response by reducing the escape probability of impact ionizing carriers due to high-energy photons. The patent pending20 detection mechanism described above involves free carrier transitions. This is different from the response observed previously from Si/SiGe QWIP detectors,107 which used transitions from bound states to either a bound split-off band state, or a continuum state which is a mixture of the light, heavy and split-off hole bands.

4.4 Split-off response of HEIWIP detectors designed for MIR

The split-off response was first demonstrated using a detector designed for the 10-15 µm range with a 20 µm threshold108, which was not designed for optimum split-off response. The detector labeled as HE0204 consisted of 16 periods of p-doped 188 Å GaAs emitters doped to 1018 cm-3

19 -3 with carbon, and 1250 Å Al0.12Ga0.88As barriers. The top and bottom contacts were 1×10 cm p- doped GaAs layers with 0.2 and 0.7 µm thicknesses, respectively. A schematic of a processed detector is shown in Figure 4.3. The measured responsivity in the 1.2-5 µm split-off range for

HE0204 at 80-130 K is shown in Figure 4.4. A peak response of 0.55 mA/W was seen at 105 K at

45 2 µm. As the temperature was further increased, the response decreased, and was not measured beyond 130 K. The increase in response with temperature may be related to phonon effects on the escape rate for excited carriers. The total quantum efficiency determined by dividing the photocurrent by the incident photon rate was ~0.04, and at 1.8 µm a specific detectivity (D*) of

2.6×104 Jones was obtain at 90K. This value is low since these detectors were designed for operation at much lower temperatures. The increased barrier in an optimized detector should reduce the dark current and hence improve D*. The two steps seen in the response at 2.8 and 3.4

µm are probably caused by the thresholds for mechanisms (1) and (2) respectively (see section

4.3). This indicates that the use of high doping is the preferred approach. Based on previous experimental results and the standard thermionic current calculations, the dark current should not increase significantly, as doping is increased until the defect assisted tunneling dominates. If the doping is kept below these high values, the absorption is increased, and therefore the response and hence the background limited infrared performance (BLIP) temperature should increase.

In order to understand the response observed using the split-off band, calculations were carried out to determine the relative absorptions for the free carrier and split-off responses. The first step was to use a k·p model, similar to that used in quantum dots,109 and quantum wells to calculate the L-H,

H-H and split-off hole energy bands. The absorption coefficient was then calculated as a function of photon energy ħω from the energy states in the band. The calculation was done for a 1 µm thick

GaAs layer that was p-doped to 3×1018 cm-3. The absorption by the split-off band was over an order of magnitude larger than for the free carrier absorption associated with the transition between

L-H/H-H bands as shown in Figure 4.5, indicating the relative improvement of the split-off mechanism in this range.

Gold p++-GaAs Contact Top Wire Contact N Periods AlGaAs of Emitter Barrier Barrier p+-GaAs Emitter

p++-GaAs Bottom Contact

Substrate

0.6 HE0204 80 K 90 K 100 K 0.4 105 K 120 K 130 K

0.2 Response (mA/W) 0.0 2345 Wavelength (µm)

48 As shown in Figure 4.6 the measured absorption increased in the split-off region compared to the expected free carrier absorption. The step seen in response at 3.4 µm is in good agreement with the calculated results shown in Figure 4.5. However, there is a small discrepancy with the drop at 2.9

µm in the calculated curve. The experimental step is ~ 0.15 µm wide, (possibly due to the effects of the photoemission process) and the threshold may be longer than it appears in Figure 4.4. The split-off response observed in a HEIWIP detector designed for threshold wavelength of ~20 µm showed a maximum operating temperature of 130 K. By reducing the free carrier threshold to ~5

µm, uncooled operation should be achieved with a D* of ~5×106 Jones. Based on above results, 3 sets of split-off band detectors were designed, grown and measured results are discussed in the following section.

4.5 Uncooled split-off detector design and experimental results

The detector structures SP1, SP2, and SP3 with three different ∆L/H values of 155, 207, 310 meV

(the corresponding Al fractions for those ∆L/H values are x = 0.28, 0.37, 0.57 giving threshold wavelengths of 8 µm, 6 µm, and 4 µm, respectively) were grown on semi- insulating GaAs substrates with a 0.7 µm thick, 1×1019cm−3 p-doped GaAs bottom contact layer, of GaAs followed

18 −3 by 30 periods of a 600 Å, undoped AlxGa1-xAs barrier, and a 3×10 cm p-doped, 188 Å GaAs emitter. The top most emitter was 0.2 µm thick and p-doped to 1×1019cm−3 in order to use as the top contact layer. The detectors were processed by wet etching to form square mesas with sides

400, 600, 800, and 1000 µm. Ti/Pt/Au ohmic contacts were evaporated onto the top and bottom contact layers. A ring contact was used on the top surface and a window was opened through the top contact for front side illumination.

Figure 4.5 The calculated absorption coefficient for the free carrier and the SO band mechanisms in a 3×1018 cm-3 p-doped GaAs layer.

0.12 HE0204

0.08

Absorption 0.04 λ2 Experiment 0.00 2345 Wavelength (µm)

Figure 4.6 Measured absorption for the sample HE0204 showing an increased absorption from the split-off transitions. The dashed line shows the expected free carrier response varying as a λ2.

51 The sample pieces with ~4 mm × 8 mm dimensions and 10 -12 different sized mesas were mounted on standard chip carriers, and gold wires were wire bonded from the top and bottom electrical connections. A schematic of a single mesa of the detector is shown in Figure 4.3. The current voltage (I-V) characteristics were measured at different temperatures from 70 to 300 K. As shown in Figure 4.7, the dark current density at 1V bias reached the same order at 140, 190 and

300 K for samples SP1, SP2, and SP3, respectively. Comparison of the measured dynamic resistance and the dark current density for the 3 samples are presented in Table 4.1. The spectral response of the detectors SP1, SP2, and SP3 were measured using a Fourier transform infrared spectrometer (Perkin-Elmer system2000) at temperatures up to 140 K, 190 K, and 300 K, respectively. Figure 4.8 shows responsivity calibrated using a bolometer for each detector under 4

V bias. These responsivities were also verified with a calibrated InGaAs photodiode at 2.5 µm.

Figure 4.9 shows the responsivity of the detector SP3 at 300 K under four different biases with the maximum responsivity of 0.29 mA/W at 300 K and 2.5 µm. The noise current density was measured using a dynamic signal analyzer (Stanford Research SR785) with the sample mounted in an optically and electrically shielded dewar. Batteries were used to bias the sample to minimize noise components from the bias source. The majority of noise is believed to be generation recombination and Johnson noise. Normalized detectivity (D*) was obtained (see Appendix A.4 for details) using the formula D*= (R × √A)/IN, where R is the responsivity (in A/W), A is the

2 -1/2 optically active area of the detector (in cm ) and IN is the noise current density (in AHz ). The calculated D* values for each sample at the optimum operating temperature is listed in Table 4.1.

The response observed in the sample SP3 at room temperature appears to be due to a single emitter without the contribution of other emitters. Modifications of the design to activate more emitters would lead to increased gain hence improved response.

100 ) -2 10-3

SP1 -6 SP2 10 SP3 at 1V bias (A cm Dark Current Density

10-9 20 80 140 200 260 320 Temperature (K)

∆ T R I D* Sample L/H max Dyn Dark (eV) (K) (Ω) (Acm-2) (Jones)

SP1 0.155 140 787 0.663 2.1×106

SP2 0.207 190 913 0.875 1.8×106

SP3 0.310 300 1138 0.563 6.8×105

SP2 190 K

2 (mA/W)

SP1 140 K 1 SP3 300 K

Responsivity 0 234 Wavelength (µm)

55 As shown in Figure 4.9, the responsivity increases with the bias up to 4 V, but increased dark current (low dynamic resistance) reduced the response above 4 V bias. Even though the reported curves are at 300 K, responses have also been observed up to 330 K by heating the sample stage using a built-in heater. At 330 K, dynamic resistance was reduced to several hundreds of ohms and the measured signal deteriorates almost to the noise level. The threshold wavelengths for the response mechanisms 1 and 2 shown in Figure 4.2 can be identified in Figure 4.9 at 2.9 µm and 3.4

µm, respectively. At 300 K, mechanism (1) becomes dominant, as can be seen by the much larger step at 2.9 µm. The threshold for the free carrier response increased slowly with temperature due to increased number of carriers above the Fermi energy, which can give response at longer wavelengths. The SP1 and SP2 detectors exhibit optimum operating temperatures at 140 K and

190 K, respectively. The higher responsivity and D* seen for longer wavelength threshold samples are possibly due to impact ionization (gain), compared to the shorter threshold samples as shown in

Figure 4.10.

4.6 Long wavelength (MIR and FIR) response observed in the split-

off detectors

In addition to the expected split-off response in 2-4 µm range, a long wavelength response was also observed for the detector SP3. The responsivity in the 2-20 µm range for various bias voltages at a temperature of 250 K and 330 K are shown in Figure 4.11 (a) and (b), respectively. This response extends to much longer wavelengths than the free carrier response threshold of 4 µm. When the incident radiation was blocked, no signal was observed. The voltage response (V/W) increased for lower operating temperature as seen in Figure 4.11(a) and (b).

SP3 0.3 300 K (1) 4 V

0.2 3 V (2) 2 V 0.1 1 V

Responsivity (mA/W) 0.0 234 Wavelength (µm)

100

-1 10 SP1 140 K SP2 150 K 10-2 SP3 150 K 10-3

-4 Responsivity (mA/W) 10

2345 Wavelength (µm)

58 The response is nearly flat above 4 µm, with small oscillations superimposed on it. The source of these oscillations is unknown at this time. The ratio of the long wave response (Rlw) to split-off response (Rsp) was increased with the temperature (Rlw/Rsp = 0.4 at 250 K and Rlw/Rsp = 1.1 at

330 K) showing that long wavelength response mechanism is dominant at higher temperatures.

This indicates the response is probably associated with changes in the thermal population of the carriers at higher temperatures. A possible explanation is that the response originates with the excited carriers in the split-off band, which is 340 meV above the light/heavy hole bands. Unlike the standard semiconductor bolometric response in which the signal is due to the increased number of electrons and holes produced through thermal generation, the signal in this detector comes from an increase in the number of carriers in the split-off band at higher temperatures. The carriers in the split-off band could then scatter into the light/heavy hole bands above the barrier and escape. The escaped carriers would then be collected by an applied electric field, contributing to the photocurrent. In this approach, the observed photocurrent would be due to heating of the sample with the corresponding increase in the current as in a bolometer, but with a different mechanism

(using the split-off band) for the change in the resistance producing the signal.

This SP3 detector was not optimized for thermal response, hence the efficiency could be further increased by making necessary modifications. The detector sample consisted of a 400 µm × 400

µm square mesa on a ~3 mm × 5 mm substrate with ~500 µm thickness. This had a large thermal mass reducing the temperature change and hence lowering the response as well as the response- speed. In addition, only a ~1 mm diameter area was illuminated and the device was not placed in an integrating cavity, as the bolometer, which greatly helps to increase the radiation incident onto the sample. By optimizing the sample size and placing it in an integrating cavity, it should be possible to improve the detector response. For a bolometer, the response is given by110

800 SP3 5 V (a) 330 K 4 V

3 V 400 2 V

1 V

Responsivity (mV/W) 0 2 6 10 14 18 Wavelength (µm)

3000 SP3 (b) 250 K 2000

5 V 1000 4 V 3 V 2 V 1 V

Responsivity (mV/W) Responsivity 0 2 6 10 14 18 Wavelength (µm)

Figure 4.11 The responsivity of the split-off detector SP3 in the 2 to 20 µm range for different bias values in the 1- 5 V range. (a) At 330 K temperature, the maximum long wavelength response was ~800 mV/W for a bias of 5 V. Peak responsivity of the split-off range was ~475 mV/W at same bias. (b) At 250 K temperature the maximum long wavelength response was ~1250 mV/W and split-off responsivity was 3000 mV/W for a bias of 5 V. The response was nearly constant over most of the range.

60 IR α R = d (4.1) GR()dl+ R where I is the current, Rd and Rl are the detector resistance and the load resistor, G is the heat flow rate, and α = (dRd/dt)/Rd is the fractional rate of change in the detector resistance. For the split-off

2 bolometer α = ∆/(kbT ) where ∆ is the split-off energy, T is the temperature, and kb is Boltzmann’s constant. The response observed for the detector corresponds to a heat flow rate of ~20 mW/K.

For a small sample size, specifically mounted for use as a themal detector, the heat flow rate can be reduced to ~15 µW/K. Using this value, if the size of the sample is assumed to be reduced so that it does not limit the response, and the sample is assumed to be in an integrating cavity so that all the radiation is absorbed, the response of the detector should be increased to ~2000 V/W.

4.7 Future Work

4.7.1 Proposed materials for split-off threshold extension

The larger doping used to obtain a high absorption in the GaAs/AlGaAs based split-off detectors has shifted the peak of the split-off absorption to below 3 µm for process (1) which is the dominant response mechanism at higher temperatures. By reducing the doping, the split-off response peak can be moved to near 3.5 µm but the response will be reduced. Hence, the use of alternate materials would be the best option. Several possible semiconductor materials, their split-off energies, and the corresponding threshold-wavelengths are listed in Table 4.2. Arsenide and phosphide would be the best materials for 3-5 and 8-14 atmospheric windows since their split-off energies fall in this range. A bandgap vs. lattice constant plot of selected arsenide and phosphide materials is shown in Figure 4.12.

Material ∆SO (meV) λSO (µm)

InP 110 11 GaP 80 16 AlP 70 18 InAs 410 3.2 GaAs 340 3.6 AlAs 300 4.1 InN 3 410 GaN 20 62 AlN 19 65 110 - 379 In Ga As P 3.3 - 11 1-x x y 1-y (0.11+0.421y-0.152y²) 93 - 101 In Ga P 12.3 - 13.3 1-x x 0.101+0.042x-0.05x2

62 By using GaAsP as the emitter, the split-off threshold (λs) could be tailored. An emitter with

GaAs0.4P0.6 should give a split-off threshold near 5 µm, allowing full coverage of the 3-5 µm range.

However, there would be significant strain between the emitters and barriers in a structure that only used GaAsP emitters and AlGaAs barriers. The strain associated with the high P fraction would introduce defects, reducing the material quality. As shown in Figure 4.12, well matched lattice

111 constants of GaP and AlP (5.4505 and 5.4510 Å ) will allow an AlxGa1-xP ternary alloy and GaP to be latticed matched for all x values from 0 to 1. Heterojunction devices with a p-GaP emitter and an AlxGa1-xP barrier on a GaP substrate should behave similarly to the well known p-

GaAs/AlGaAs system. The free carrier threshold of the p-GaP/AlxGa1-xP system can be tuned to

GaP split-off energy of 80 meV (16 µm) by changing Al fraction x but still keeping lattice matched conditions. Growth of these structures should not be a difficult task since characteristics of GaP/AlGaP heterojunctions,112-114 superlattice,115 heterostructure based detectors,116 and solar cells117 have already been reported. Processing of these devices will also be straight forward since different etching methods for GaP/AlGaP have also been developed.118-120

121-123 124- The In1-xGaxAsyP1-y lattice match to InP has been well studied and widely used as QWIP

127 128 129,130 , transistor , LED, and laser structures. The split-off energy of In1-xGaxAsyP1-y can be tuned for a wide energy range from 0.11 to 0.379 eV (3.3 – 11 µm) by changing the As alloy

123 fraction y from 0 to 1 (ESO = 0.11 + 0.24y) . Hence, a detector with p-InGaAsP emitter and InP barrier would be a potential choice for a tunable split-off threshold from ~3 –11 µm. Since the

111 valence band discontinuity of the In1-xGaxAsyP1-y/InP heterostructure can be expressed as

2 ∆EV = 0.502y-0.152y , the free carrier threshold wavelength will also be tunable. However, in order to achieve similar or ~10% less ∆EV compared to the ESO, “y” should be with in 0.5 - 0.7 range. This corresponds to a threshold wavelength in the 4-5 µm range.

AlP Direct gap 2.4 AlAs Indirect gap GaP

1.6 InP

GaAs

0.8 Energy Gaps (eV)

InAs 0.0 5.4 5.6 5.8 6.0 Lattice Constants (Å)

Figure 4.12 Band gap and lattice constant of selected III-V semiconductors (data were taken from “Handbook series on semiconductor parameters111”.) Solid lines represent direct band region and dashed lines represent indirect band region. GaP/AlGaP would be a high-quality, lattice matched system similar to GaAs/AlGaAs. Also, InGaAs and InGaP can be lattice matched to InP and GaAs, respectively.

0.4 Eso (eV) 0.3 ∆Ev (eV)

0.2 Energy (eV) Energy 0.1

0.0 0 0.2 0.4 0.6 0.8 1

As fraction y

++ 600 Å p -In0.3Ga0.7As0.4P0.6 contact

Al0.3Ga0.7As barrier 400 Å p+-In Ga As P emitter 200 Å BC 0.3 0.7 0.4 0.6

Al0.3Ga0.7As barrier

++ p - In0.3Ga0.7As0.4P0.6 contact 700 µm

GaAs substrate

Figure 4.14 Schematics of the In1-xGaxAsyP1-y emitter and Al0.3Ga0.7As barrier based detector structure, which is lattice matched to the GaAs substrate.

66 A calculated ∆EV and ESO for different Arsenic fractions y is shown in Figure 4.13. In order to keep lattice matched condition with InP, the x ≈ 0.47 y condition should be satisfied. It is possible to grow InGaAsP with the In and P fractions chosen so that structure would be lattice matched to

GaAs131-133. This would allow the freedom in tailoring the barrier by the use of AlGaAs. A device with In0.3Ga0.7As0.4P0.6 would be lattice matched to GaAs and would have a split-off threshold of

5.1 µm for process (1), which is the dominant split-off mechanism (see Figure 4.2). The barriers in an optimized detector are expected to be Al0.30Ga0.70As to reduce the dark current. Thus the device

18 -3 structure would consist of 3 × 10 cm doped, 200 Å In0.3Ga0.7As0.4P0.6 emitters and 400 Å

Al0.30Ga0.70As barriers. A schematic digram of the detector structure is shown in Figure 4.14.

4.7.2 Dual-band detector design for the 3-5 and 8-14 µm atmospheric

windows

A dual-band split-off detector is proposed for the practically important atmospheric windows in the

3- 5 µm and 8- 14 µm ranges. This structure is based on the well studied134-142, lattice matched,

GaAs/In1-xGaxP/AlGaAs material system. In1-xGaxP/AlGaAs/GaAs heterojunction based transistors143-146, diode lasers147,148, and tunnel diode based solar cells149-151 have been reported. The lattice constant and band gap of In1-xGaxP can be expressed as 5.8687-0.4182x and 1.34 + 0.69x +

2 111 0.48x (for x < 0.63), respectively (see page 38 of Ref ). In0.49Ga0.51P would be lattice matched to

GaAs with a band gap Eg of 1.81 eV and spin-orbital splitting ∆SO of 0.109 eV (11.3 µm). The idea is to use the p-GaAs/AlGaAs emitter barrier system to detect the 2 - 5 µm range and to use the p-In0.49Ga0.51P/AlGaAs emitter barrier system to detect the 8-14 µm range. A schematic of the detector structure is shown in Figure 4.15, and the band diagram under a biased condition is shown in Figure 4.16. This three-contact device architecture was previously reported152 for a GaN/AlGaN,

UV-IR dualband system, and it allows simultaneous identification of each wavelength band.

p++-GaAs contact 3-5 µm Al Ga As barrier Response 0.57 0.43 p+-GaAs emitter p++-InGaP emitter Al0.57Ga0.43As barrier MC p++-GaAs contact 8-14 µm Al0.8Ga0.2As barrier Response + p -In0.49Ga0.51P emitter BC Al0.8Ga0.2As barrier

++ p -In0.49Ga0.51P contact

GaAs substrate

Figure 4.15 Proposed dual-band detector structure for the 3-5 and 8-14 µm atmospheric windows. A three-contact design will allow the separate detection of 3-5 µm radiation from the top to middle contact (TC – MC) and 8-14 µm range radiation from the middle to bottom contact (MC – BC). The Al fractions of the barrier (0.57 and 0.8) were selected so that the barrier height is equal to the split-off energy of the emitter layer.

p++-GaAs p+-GaAs MC p++-GaAs TC P 0.51 P As Ga 0.51 0.43 As As 0.49 Ga Ga 0.2 0.43 -In 0.57 0.49 + Ga As Ga Al p 0.8 0.2 BC -In 0.57 ++ Al Ga Al p 0.8 Al

69 As shown in Figure 4.15, first, the highly p doped, In0.49Ga0.51P (lattice matched to GaAs) contact layer will be grown on GaAs substrate. Next the Al0.8Ga0.2As barrier, In0.49Ga0.51P emitter, and

Al0.8Ga0.2As barrier are designed to have a 0.088 eV barrier height, which is similar to the split-off energy of the In0.49Ga0.51P emitter layer. This relatively high Al fraction should not introduce growth difficulties since AlGaAs with an 80% Al fraction has already been reported153-158. A highly doped, GaAs middle contact layer is followed by Al0.57Ga0.43As/p-GaAs/Al0.57Ga0.43As

(barrier/emitter/barrier) layers that are grown on top of the last barrier to achieve a 0.248 eV barrier.

4.8 Conclusion

An uncooled infrared detector based on a GaAs/AlGaAs multiple heterostructure was reported.

The response is primarily from heavy/light hole to split-off transitions, and the detector showed a peak D* of 6.8×105 Jones at 2.5 µm 300 K. As a well-developed material system, GaAs is a feasible solution to future uncooled infrared detection; hence high quality growth and integration with other readout electronics is readily available. Materials other than GaAs/AlGaAs may help to extend the coverage to longer wavelengths. Possible materials such as phosphides (with a threshold of ~18 µm) and nitrides may be able to operate at 60 µm or beyond at elevated temperatures. A possible dual-band detector design was proposed to cover 3-5 µm and 8-14 µm atmospheric windows using a combined system with arsenides and phosphides. The response can be optimized by using a graded-heating-barrier that reduces trapping and increases the gain. Another optimization method would be the use of surface plasmon resonances in metallic nanoparticles deposited on the detector surface159. A properly optimized device working at room temperature may compete with currently available uncooled detectors160,161. The long wavelength response

70 observed in the split-off detector is due to a thermal mechanism. This mechanism involves a new type of bolometric response, based on the increase in carriers in the split-off band for p-type material. These carriers are free to be transported through the detector, producing the photo-signal.

This is a new approach to bolometer development and could lead to improved detectors. By using other materials, the operating temperature can be optimized for the desired response wavelength range. These detectors offer an interesting new approach to MIR and FIR detection at high temperature, and could lead to many new applications.

71 Chapter 5

GaSb homojunctions for Far-IR (THz) detection

5.1 Introduction

Much of the recent interest in terahertz (THz) frequency radiation between 10 to 0.3 THz (30 µm to 1 mm) stems from its ability to penetrate many organic materials without the ionizing damage associated with short wavelength radiation such as X-rays162. Another important feature is the fact that THz radiation is readily absorbed by water. This allows THz radiation to distinguish between materials with varying water content, for example, fat versus lean meat. These properties offer various applications related to process and quality control, as well as biomedical imaging30.

Moreover, tests are currently under way to determine whether THz tomographic imaging can augment or replace standard mammography. Others have proposed THz imaging as a method of screening passengers for explosives at airports. For military and astrophysics uses, THz detectors have many applications such as early detection of long range missiles, concealed weapon identification and space based astronomy. Those studies explain the reasons for the surging demand for high performance THz detectors in recent years.

Charge transport properties163 and THz absorption164 of high quality GaSb films were reported elsewhere. Infrared (IR) detectors based on type II InAs/GaSb superlattices165 have been

72 demonstrated for the 3-5 µm166 and 8-12 µm167 transparency bands of the atmosphere. The longest zero response threshold wavelength reported was 20 µm168.

5.2 GaSb homojunction detector mechanism

The active region of a Homojunction Interfacial Workfunction Internal Photoemission (HIWIP) detector consists of one or more periods, each consisting of a series of doped emitter and undoped barrier layers. In HIWIP detectors, the incident photons are absorbed in the emitter layers by the free carrier absorption mechanism, and under suitable bias conditions the photoexcited carriers with energy hν larger than the band-edge offset between the doped emitter layer and the undoped barrier region are emitted across the junction and then collected. For a homojunction, the band offset is determined by the doping-induced bandgap narrowing of the emitter105. The internal photoemission of the carriers is characterized by the interfacial work function ∆ which corresponds to the energy difference between the bottom of the barrier (for a p-HIWIP) and the Fermi level in the emitter. In general these detectors show broad band response due to free carrier absorption which involves initial and final energy states within the same continuum. The zero-response threshold frequency, f0 is introduced only in the photoemission stage. Therefore, the threshold frequency of the detector is f0 = 0.242∆ with f0 in THz and ∆ in meV, or the zero-response threshold wavelength of the detector is λ0 = 1240/∆ where λ0 is in µm and ∆ in meV.

5.3 Experimental Design

The HIWIP structure was grown on a GaSb substrate at a temperature of 600 °C and a reactor pressure of 400 Torr by metal-organic vapor phase epitaxy169 using a Thomas Swan vertical reactor. Conventional trimethylgallium and trimethylantimony were used as precursors. The

73 structure of the detector, grown on a 0.7 mm thick, 5×1018 cm-3 p-doped, GaSb substrate, consisted of a 0.05 µm thick, 2×1018 cm-3 p-doped, bottom emitter, a 2 µm thick undoped barrier, a 0.05 µm thick, 2×1018 cm-3 p-doped, top emitter, and a 0.1 µm thick, 5×1018 cm-3 p-doped, top contact. Zinc was the dopant, with diethylzinc used as the dopant source. The detector was fabricated by etching different size mesas using wet etching techniques. Ti/Pt/Au ohmic contacts were evaporated for both the top and bottom contacts. A schematic view of the processed detector and its relevant band diagram is shown in Figure 5.1.

5.3.1 Dark current, responsivity and noise measurements

Dark and 300 K background current voltage (IV) characteristics of the sample were measured at various temperatures using a Keithley 2400 source meter with the sample mounted on the cold finger of a closed cycle refrigerator. The spectral response measurements were carried out using a

Perkin-Elmer System2000 Fourier-transform infrared (FTIR) spectrometer with a Si composite bolometer as the reference. The sample was mounted in a liquid He dewar made by Infra-Red

Laboratory Inc. The same setup was connected to a SR-785, two-channel, fast Fourier transform signal analyzer coupled to a SR-560, high impedance, low-noise, voltage preamplifier for noise current density measurements.

5.4 Results and discussion

The sample GSU-A3 contains square mesas with sides of 400, 600, 800, and 1000 µm. The measured dark current density variation for 8 different mesas of the sample at 10 K is shown in

Figure 5.2. Current densities are almost the same for different size mesas of untreated samples, showing that it is free of major side-wall/surface leakage.

(a) Metal contact 0.1 µm 5×1018 cm-3 p++

0.05 µm 2×1018 cm-3 p+ emitter

2 µm Undoped-GaSb barrier

0.05 µm 2×1018 cm-3 p+ emitter

5×1018 cm-3 p++ GaSb Substrate

(b) Bottom Contact GaSb + p GaSb Top Contact GaSb + p V E ∆ ∆

-1 10 T = 10 K GSU-A3

-3 10

T = 4.9 K

-5 10 Current Density (A/cm²) Density Current

-7 10 -4-2024 Voltage (V)

Figure 5.2 The dark current density vs. bias voltage for 8 different mesas in sample GSU-A3 measured at 10 K shows good uniformity of the structure. A single dark IV curve for one mesa at the 4.9 K spectral measurement temperature is also shown.

76 Normally larger devices (400 - 1000 µm) are not affected very much by surface leakage, which often occurs for devices less than about 50 × 50 µm. The dark current density for an 800 µm mesa at 4.9 K is also shown in Figure 5.2. The measured responsivity of GSU-A3 under different bias voltages and over the wavelength range 20-44 µm is shown in Figure 5.3. An increase in responsivity can be observed for applied bias increasing up to a field of 18.5 kV/cm (3.7 V), but above this field the responsivity started to saturate. The maximum response, 9.7 A/W, was obtained at 36 µm under a 3.7 V bias. The detector shows a maximum detectivity of 5.7×1011

Jones at a 3V bias. Above this voltage, the noise current is higher due to the low dynamic resistance of the sample, reducing the detectivity at a 3.7 V bias. The responsivity decreases with increasing operating temperature, and no significant signal could be measured above 15 K. The responsivity drops to zero around 43 µm due to the reststrahlen band of GaSb. The detector responsivity from 20 µm to 200 µm for 1V, 2V and 3V biases is shown in Figure 5.4. The corresponding background noise level (in the bottom of Figure 5.4) was measured after blocking the IR beam of the FTIR spectrometer by using a thick metal plate. Above the reststrahlen absorption minimum at 43 µm, the response initially increases and then gradually decays up to the

97 µm threshold. At lower frequencies, (longer wavelengths) the sample shows a clear but low flat response up to 1.5 THz (200 µm).

This response is relatively low compared with the peak response at 8.3 THz (36 µm) but clearly an order of magnitude above the noise level. The 20 µm to 43 µm photoresponse does not exhibit any dependence on measurement speed (optical path difference velocity of FTIR) however the constant long wavelength tail (43 – 200 µm) response increases with decreasing measurement speed. A second sample processed in a different laboratory displayed a similar flat response long wavelength tail, confirming that it is not processing or contact related.

Frequency (THz) 1510 7 10 T = 4.9 K

8 3.7 V 3.4 V 3.0 V 6 2.0 V 1.0 V

4 Responsivity (A/W) Responsivity Responsivity (A/W) Responsivity

0 20 30 40 Wavelength (µm)

Frequency (THz) 154 2 1.5 101 T = 4.9 K

0 10 3.0 V 2.0 V 97 µm -1 1.0 V 10

-2 10 Responsivity (A/W) Responsivity (A/W)

-3 10

-4 10 20 80 140 200 Wavelength (µm)

The zero response threshold wavelength λ0 of the detector is not clearly visible, since it corresponds to two different overlapping response mechanisms. The free carrier threshold of λ0 = 97 µm (arrow in Figure 5.4) was obtained by selecting the intersection point of the flat long wavelength response with the free carrier response. This value agrees well with the calculated Arrhenius ∆ value. Figure

5.5 shows the ln(I/T1.5) vs. 1/T plot that was used to calculate the internal workfunction ∆. The long wavelength flat response mechanism is not yet clearly understood.

The response time of the detector can be estimated from the bias dependent responsivity measurements170,171. For low experimental temperatures (T ~ 4.2 K), the current responsivity R at a bias voltage V can be expressed as

31qηµτ RV= 2 (5.1) 2dkTB 0 where q is elementary charge, η is the absorption quantum efficiency, µ the mobility, kB is the

Boltzmann constant, d the detector thickness, T0 is the equilibrium temperature and τ is the energy relaxation time of the hot carriers. The energy relaxation time could give the lower limit for the detector response time, and could be regarded as the response time for an ideal detector. The bias dependence of the responsivity measured at 4.9 K is shown in Figure 5.6. At low voltages (V <

2.5V) the responsivity increases linearly with bias. For both intrinsic and extrinsic photoconductive detectors at a given bias, the responsivity is proportional to the response time. The absorption quantum efficiency η can be expressed as described in Ref 170 as

1− e2αl (5.2) η = . e(/dLZ )

-10 y = -157.208x - 7.108 R2 = 0.998

-12 ) 1.5 ln(I / T -14

-16 0.02 0.04 0.06 1/T (K-1)

Figure 5.5 Arrhenius curve of the sample showing slope of -157.2. The internal workfunction ∆ of 12.8 ± 0.3 meV was calculated using this slope.

81 Here α, l and Lz are the absorption coefficient, thickness of the emitter layer, and inelastic

164 scattering mean free path, respectively. Using the GaSb α from Ref. and taking Lz as 1 µm, the total absorption quantum efficiency was calculated as 17.3%. Using a detector thickness d of 2.1

µm, the measured mobility164 of 200 cm2/Vs for similar doping levels, and the slope of 1.6 A/WV measured from the linear region (0 - 2.5 V) of R vs. V plot, the response time of the detector is estimated to be of the order of a few picoseconds. The photocurrent gain values g are calculated for the peak response (36 µm) as 0.6 at 2 V and 1.9 at 3.7 V biases from the combination of

R=qηgλ/hc with Eq.(5.2) , where h, c, and λ are the Planck constant, speed of light, and wavelength at peak response. The effective quantum efficiency ηg was calculated as 10 and 33 for 2 V and 3.7

V biases, respectively. The above photocurrent gain numbers and calculated shot noise gain104 numbers differ for this sample. This difference and the unusually high impedance of the sample are believed to be due to the Schottky type contacts172 . Further studies are needed to examine the effects of Schottky contacts on HIWIP detectors.

5.5 Conclusion

GaSb based, HIWIP detectors with a 97 µm (~3 THz) zero response threshold wavelength were demonstrated. The detectors have a peak responsivity of 9.7 A/W and peak detectivity of 5.7×1011

Jones at 4.9 K. In this study a simple single emitter / barrier structure was utilized. The high response observed could be further enhanced by using multilayer structures which will increase the photon absorption efficiency and could possibly induce photocurrent gain enhancement173. The doping offset of the emitter and barrier determined the threshold of the HIWIP detector. Using

Heterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) structures104 like

InxGa1-xSb/GaSb would give a flexible system to control the threshold.

10 4 Slope = 1.61 ± 0.06

) 8 2

6 Response (A/W) Response 0 012 4 Bias (V)

Peak (A/W Responsivity 2

0 01234 Bias (V)

Figure 5.6 The bias dependence of the peak responsivity at 4.9 K. The responsivity was almost linear (with a slope of 1.61 ± 0.06 A/WV) for low biases (< 2.5 V).

83 Estimations show that with the variation of the In fraction, a 1 THz (300 µm) threshold could be achieved while keeping the accuracy of the In fraction in the practical range (a variation of 2.5% will only change the workfunction by 1 meV). One of the major problems in achieving a 1 THz threshold with GaAs/AlGaAs or GaN/AlGaN system is the need for very high Al fraction accuracy

(0.2% for AlGaAs and 0.05% for AlGaN) that is at or beyond the edge of the experimental capabilities. Therefore, GaSb/InGaSb is a promising material for THz detection. Resonant cavity enhanced GaAs/AlGaAs HEIWIP’s have already been demonstrated174 and resonant cavities can be easily incorporated into GaSb based detectors to further enhance the response.

84 Chapter 6

Summary and conclusion

Here relative merits of each of the techniques discussed before are presented. The four chapters in the dissertation presented four different infrared detection concepts with the experimental results to verify each concept. First two chapters discussed an amorphous semiconductor (TiO2, CuSCN, and

PbS) based devices and the other two chapters discussed detection based on epitaxially grown crystalline semiconductors (GaAs, AlGaAs, and GaSb). All experimental results presented in previous chapters are summarized in Table 6.1.

The detectors based on dye-sensitized nanostructures and colloidal quantum dots utilized simple growing techniques such as screen printing or spray pyrolysis hence relatively inexpensive and can also be fabricated on curved surfaces or flexible substrates. DSNIRD’s followed the same principle as DSSC known as Gratzel’s solar cell but in this case, the liquid electrolyte was replaced with a solid hole collecting (p-type) semiconductor CuSCN. Commercially available IR sensitive dyes used in these initial experiments are not optimized for dye-sensitization. Not only the HOMO and

LOMO levels of the dye but also the bonding and charge transfer properties of the dye with the semiconductor layers play major roll on the conversion efficiency of the device.

IR783 0.4 - 0.9 (0.808) 0.4 0.06 1.4×1010 300 MC-IR792 0.4 - 0.95(0.812) 2.7 0.41 9.5×1010 300 IR820-IR1040 0.4 - 1.1 (0.858) 1.0 0.14 3.5×1010 300 DSNIRD21 IR820 0.4 - 0.95(0.866) 0.3 0.04 1.1×1010 300 BPR-IR820 0.4 - 0.97(0.876) 1.1 0.16 3.9×1010 300 BPR-IR1040 0.4 - 1.2 (1.056) 0.3 0.04 1.1×1010 300 CQD25 PbS-300 0.4 -1.1(540) 195 V/W - 3.0×108 300 SP1 1.5 - 4 (2.5) 2.3 0.11 2.1×106 140 Split-off24 SP2 1.5 - 4 (2.5) 2.7 0.13 1.8×106 190 SP3 1.5 - 4 (2.5) 0.29 0.01 6.8×105 300 GaSb GSU-A3 20 - 97(36) 9700 33 5.7×1011 4.9 HIWIP26

86 This study was not intended to modify the chemical structure and synthesis optimized dyes for IR range sensitization. Instead, several different anionic compounds were used to improve the binding property of cationic dyes to the semiconductor. The observed peak conversion efficiency ~0.4% at

812 nm is relatively low compared to properly optimized dyes for visible wavelength such as Ru-

N3 with experimentally proven 10% conversion efficiency. DSCS is a rapidly developing research area and new findings in DSSC field can be directly incorporate to improve the performance of

DSNIRD’s. These detectors have the advantage of not being sensitive to thermal noise and radiation that initiate bandgap excitations. Despite quite low conversion efficiency the peak specific detectivity (9.5 ×1010 Jones at 812 nm) measured was comparable to commercially available Si or InGaAs photodiodes due to the low noise level of the DSNIRD’s. Due to the dye degradation especially when UV radiation is present, the life time of the DSNIRD’s is low compared to Si or InGaAs. Properly sealed detectors eliminate moister with a UV protective coating on front window will resolve the two issues.

PbS CQD embedded capacitor type detector demonstrate during this study reveal a novel detection mechanism without direct contact to QD or quantum wires which shows optically generated electronic polarizability. Low cost fabrication process and wavelength tunability by changing size of the QD, and fabrication possibility on flexible substrates are the attractive features of these detectors. However observed detectivity values are two orders of magnitude lower than currently available detectors. In order to increase responsivity QD density inside the capacitor should be increased. However in general conductor-insulator composites exhibit percolation thresholds when the packing fraction of the conducting material exceeds a critical value. Therefore QD density cannot be increased arbitrally. CQD capacitor based detector needed an optical chopper or modulated incident radiation since these detectors are sensitive only to a change in the intensity.

87 This is not practical for some applications. Finally the growing techniques of DSNIRD’s and CQD based detectors are not directly compatible with standard Si readout electronic processing, direct integration may not be possible at the current state-of-the-art. Further research will be needed to develop detector arrays and integration methods. In other words both detectors are more suitable for low cost large area single element detectors instead of detector arrays for imaging applications.

GaAS/AlGaAs heterojunction based split-off band detectors and GaSb homojunction based THz detector discussed in chapter 4 and 5 are III-V semiconductor based structures grown by molecular beam epitaxy, or metalorganic chemical vapor deposition techniques. Split-off band detector utilize the heavy hole light hole transition for response and the free carrier threshold for perform tailoring.

The split-off transition will be fixed for a particular material. Different materials can give rise to different response regions, due to the split-off energy differences. Using bandgap engineered III-V materials such as InGaP and InGaAsP, split-off detectors could be develop covering the wavelength ranges from 3-12 microns. This approach gives the additional controllability of the operating temperature, responsivity and specific detectivity by tuning the free carrier threshold.

Three different set of samples with λt to split-off energy ratio 42%, 57%, and 85% (sample SP1,

SP2, SP3 respectively) were tested during this study. Operating temperature increased with λt to split-off energy ratio as expected. The highest operating temperature of 330 K was observed for

SP3 with an 85% λt to split-off energy ratio. According to those results 77% λt to split-off energy ratio will be the best for 300 K room temperature operation. Room temperature detectivity observed in the sample SP3 is quite low compared to available competitors such as InGaAs photodiodes. As a well-developed material system, GaAs is a feasible solution to future uncooled infrared detection; hence high quality growth and integration with other readout electronics is readily available.

88 GaSb has a higher free carrier absorption coefficient at THz frequencies compared to the GaAs.

Therefore it is a promising material for THz detectors. GaSb /InGaSb HEIWIP detector have advantage over GaAs/AlGaAs system of tailoring λt to very long wavelengths still keeping a higher In fraction which is not possible with GaAs/AlGaAs system. GaSb is not a well developed material system such as GaAs, Si, or Ge. A GaSb homojunction based THz detector was analyzed as an initial study to test the quality of the material and processing. The first set of samples showed

(see the Table 6.1) comparable detection parameters with available other detectors such as

HgCdTe and Si composite bolometers. Both the split-off band detectors and GaSb HIWIP detectors shows long wavelength flat response which is not expected at from the free carrier response. This can be identified as a bolometric type response since the response is highly measurement speed dependent. Future research needed to optimized these response and compare with available bolometers.

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111 Appendix A

Detector characterization

A.1 Responsivity (Photo Sensitivity)

Responsivity is the output current (or output voltage) per watt of incident power when noise is not a consideration.

S R = (A.1) PA

where S is the signal output [A or V], P is the incident light intensity [W/cm2], and A is the detector active area [in cm2].

A.1.1 Spectral response measurements and responsivity calibration

The samples responding in the UV, VIS or NIR range was measured using a monochromator and lock-in-amplifier setup (see details in Appendix B). A Si photodiode and an InGaAs photodiode with a known responsivity curves were used to calculate the spectral responsivity of the sample.

The samples responding in the MIR and FIR range were measured using a Perkin Elmer System

2000 Fourier Transform Infrared (FTIR) Spectrometer and a Si bolometer was used to calculate responsivity spectra. The measurement procedure involves two measurements: sample spectra

112 (VS(λ)) and bolometer or calibrated Si or InGaAs photodiode spectra (VCD(λ)). Those two spectra are obtained concurrently with the same combination of optical windows, beamsplitter, and filters, so that the optical path is identical. The voltage responsivity can be obtained using

GVS ()λ RRVCD()λ = ()λ . (A.2) VCD ()λ

Here G is the geometrical factor, which corrects for differences in the radiation-incident-area of the detector and the bolometer/photodiode and RCD is the sensitivity curve given by the manufacturer.

To obtain the current responsivity, the voltage responsivity is divided by the effective resistance.

As the detector and the load resistor act as a voltage divider for the photocurrent, the effective resistance Re is the parallel combination of the load RL and the detector dynamic resistance Rd = dV/dI, yielding Re = RL×Rd/( RL+Rd). Therefore, the current responsivity can be express as

GVSCDLd()λ R ()λ ( R+ R ) RI ()λ =× (A.3) VRRCD()λ L d

A.2 Quantum efficiency (η)

The photocurrent of the detector for given wavelength λ can be expressed as

PAqgPAη λ Iqg==η SC c (A.4) h hc λ

113 where λ is the wavelength, h is Planck’s constant, c is the speed of light and q is the electron charge. The quantum efficiency η is the number of electron hole pairs generated per incident photon, and the gain, g, represents the number of carriers collected at the contact per one generated carrier.

Thus, the current responsivity is

ISC ηqgληλ g R ()λ == = (A.5) I PA hc 1.24 if λ is measured in µm and RI in A/W. The relation with quantum efficiency η is as follows:

RI ()λ η =×1.24 100% . (A.6) λg

A.3 Noise Equivalent Power (NEP)

The incident light power needed to produce an output signal equal to the intrinsic noise level of the detector is

PA NEP = (A.7) SN/.∆ f where N is the noise output and ∆f is the noise band width.

114 A.4 Specific Detectivity (D*)

The specific detectivity, a figure of merit used to characterize performance of a detector, is equal to the reciprocal of noise equivalent power, normalized to unit area and unit bandwidth and is given by

* SN/.∆ f A RI . A D ===. (A.8) PANEP N/ ∆ f

The noise current density Nd can be measured using a noise spectrum analyzer and is expressed as

N 2 N = . (A.9) d ∆f

Thus D* can be calculated using following formula

*1/2RA D = I [cm Hz /W] . (A.10) Nd In general, the measurement conditions of D* are expressed in the format of D*(a, b, c), where “a” is the temperature [K] or wavelength [µm] of a radiant source, “b” is the chopping frequency, and

“c” is the bandwidth.

A.4.1 Noise measurements and detectivity calculation

The D∗ of the devices at different temperatures and applied biases is obtained from the measured responsivity (RI), noise current density (Nd), and the illuminated area of the detector (A). The later are measured with a dual channel Fast Fourier Transform (FFT) signal analyzer and a SR570 low

115 noise current pre-amplifier, as shown in Figure B.15. A thick copper plate at the device temperature is used as the radiation block to provide the dark conditions for the measurements. The value of D∗ is calculated from the above equation.

116 Appendix B

Software development with Microsoft Visual

Basic

B.1 Multi-sample I-V-T characterization software

An in-house software program was developed to automate the detector I-V-T (current vs. voltage under different temperatures) characterization process. The software controls a Keithley 2400 source meter, a Keithley 7001 switch sysytem, a SI-9620 temperature controller (for a Helium closed-cycle refrigerator) through the GPIB interface. The system is capable of recording I-V curves of up to 10 samples in a user defined voltage range, temperature range, and step size. In general, a closed–cycle refrigerator is capable of working from 7 K up to 330 K in temperature.

User selectable options allow the user to save data directly in a Microsoft Excel file or ASCII text files. As a additional feature the user can enable current vs. time data recording at a fixed voltage, for studying transient characteristics of the sample. The following figures show the user interfaces and main program windows. Source codes for each form and subprograms are listed in the next subsection.

117 B.1.1 I-V-T setup instrument configuration

Source meter es under different temperatures Switch System Switch IVT :vs. Voltage Current curv Refrigerator Up to 10 samples can be connected He Closed Cycle mounted inside this inside Samples are

Figure B.1 The block diagram of the I-V-T setup showing GPIB communication connections (red lines with arrowheads) and other sample wirings (blue lines).

118

Figure B.2 Photograph of the IVT setup showing Keithley 2400 source meter, 7001 switch system, SI-9620 temperature controller (top) and helium closed cycle refrigerator (bottom).

119 B.1.2 User interfaces of the I-V-T software

120

121

122

123

Figure B.7 The I-V-T mode main screen showing the active sample graph in the left window and the sample temperature variation with the time in the right window.

124

Figure B.8 The temperature vs. time plot for the I-V-T mode. Red circles indicate the measurement starting point.

125

Figure B.9 The control panel for the Keithley 2400 source meter. The user can use this to find scanning voltage limits based on a specified current level for their samples.

126

127

128 B.1.3 Flow chart for the IV opration mode

(Kethley 2004 source meter, 7001 switch system)

Start basic IV

Input (10) parameters Find the best scan range from user / or use for user selected current default values limit

Set Source-Meter to “source” voltage and “measure” current mode Set current limit Set Voltage to the starting point

Yes

Take user defined # of readings No Slope grater than with the user entered delay the defined value?

I vs. t Yes Gradient plot On? Calculate the slop check ON? Yes No Plot I vs. t Data Calculate the average value

Plot Data Save data

Last voltage No Set the next voltage value? value

Yes

No Reached Yes No Sweep the # of ON? Sweeps ?

Yes End

129 B.1.4 Flow chart for the multi sample IVT operation mode

(Kethley 2004 source meter, 7001 switch system)

Start IVT

Input parameters from user

Set temperature controller for the starting temp. (Tset)

Plot T vs. t Read the sample Data Wait for the Temperature (Tsample) specified delay time

|Tset - Tsample| < tolerance? No Save T vs, t

Yes

Switch the first sample conection to the Source-Meter

Do the basic IV (while monitoring Tsample)

All samples No Switch to the next scanned? sample

Yes

Set temperature No Reached the Yes controller to the next last temp End value setting?

130 B.1.5 Source code

*********************************************************************** Module1.bas *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Public fMainForm As frmMain Public IVTMode As Boolean 'If current running mode is IVT then IVTMode is true

Sub main() InitializeSM InitializeSW InitializeTC frmSplash.Refresh Set fMainForm = New frmMain Load fMainForm Unload frmSplash fMainForm.Show frmMessage.Show End Sub

Sub SaveSetings() fn = FreeFile() Open "IVtSettings.inf" For Output As #fn Print #fn, GPIBSM End Sub

Sub Wait(Time_in_seconds As Single) st = Timer While Timer - st < Time_in_seconds DoEvents Wend End Sub

*********************************************************************** GPIB_commands.bas *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Const ARRAYSIZE = 1024 ' Size of read buffer Dim ErrMsg As String * 100 Dim ErrorMnemonic Dim ValueStr As String * ARRAYSIZE Dim Response As Integer Dim DevSW% Dim DevSM% Dim DevTC% Public GPIBSM As Integer ' source meter GPIB address Public GPIBSW As Integer ' Switch GPIB address Public GPIBTC As Integer ' Temp. Controller GPIB address

131 'To write command to KEITHLEY 2400 Source Meter Sub SendSM(CommandString, stat%) ilwrt DevSM%, CommandString, Len(CommandString) If (ibsta And EERR) Then stat% = 1 Call GPIBCleanup("Unable to write to KEITHLEY 2400 SourceMeter", DevSM%) Else stat% = 0 End If End Sub

'To write command to KEITHLEY 7001 Switch system Sub SendSW(CommandString, stat%) ilwrt DevSW%, CommandString, Len(CommandString) If (ibsta And EERR) Then stat% = 1 Call GPIBCleanup("Unable to write to KEITHLEY 7001 Switch system", DevSW%) Else stat% = 0 End If End Sub 'To write command to SI 9620-1 Temperature controler Sub SendTC(CommandString, stat%) ilwrt DevTC%, CommandString, Len(CommandString) If (ibsta And EERR) Then stat% = 1 Call GPIBCleanup("Unable to write to Temp. Controller", DevTC%) Else stat% = 0 End If End Sub

'To read Data from KEITHLEY 2400 Source Meter Sub ReadSM(r$) ilrd DevSM%, ValueStr, Len(ValueStr) If (ibsta And EERR) Then Call GPIBCleanup("Unable to read from device", DevSM%) End If r$ = ValueStr End Sub

'To read Data from 7001 Switch system Sub ReadSW(r$) ilrd DevSW%, ValueStr, Len(ValueStr) If (ibsta And EERR) Then Call GPIBCleanup("Unable to read from device", DevSW%) End If r$ = ValueStr End Sub

'To Queries Temp. Controller SI 9620-1 settings Function ReadTC(CmdString As String) ilwrt DevTC%, CmdString, Len(CmdString) If (ibsta And EERR) Then Call GPIBCleanup("Unable to write to device", DevTC%)

132 End If ilrd DevTC%, ValueStr, Len(ValueStr) If (ibsta And EERR) Then Call GPIBCleanup("Unable to read from device", DevTC%) End If ReadTC = ValueStr End Function

' To close required channel Sub CloseSW(j As Integer, MidGNDMode As Boolean) SendSW ":open all", stat% If j < 1 Or j > 10 Then Exit Sub cl$ = ":clos (@ 1!" & Trim(Str(j)) & ", 1!" & Trim(Str(j + 10)) & ")" SendSW cl$, stat% If MidGNDMode = True Then SendSW ":clos (@ 1!22)", stat% Else SendSW ":clos (@ 1!21)", stat% End If End Sub Sub InitializeSM() GPIBSM = GetSetting(App.Title, "Settings", "GPIBSM", 18) DevSM% = ildev(0, GPIBSM, 0, T10s, 1, 0) If (ibsta And EERR) Then ErrMsg = "Unable to open KEITHLEY 2400 Source Meter" & Chr(13) & "ibsta = &H" & _ Chr(13) & Hex(ibsta) & "iberr = " & iberr MsgBox ErrMsg, vbCritical, "Error" Exit Sub End If ilclr DevSM% End Sub

Sub InitializeSW() GPIBSW = GetSetting(App.Title, "Settings", "GPIBSW", 7) DevSW% = ildev(0, GPIBSW, 0, T10s, 1, 0) If (ibsta And EERR) Then ErrMsg = "Unable to open KEITHLEY 7001 Switch system" & Chr(13) & "ibsta = &H" & _ Chr(13) & Hex(ibsta) & "iberr = " & iberr MsgBox ErrMsg, vbCritical, "Error" Exit Sub End If ilclr DevSW% End Sub

Sub InitializeTC() GPIBTC = GetSetting(App.Title, "Settings", "GPIBTC", 24) DevTC% = ildev(0, GPIBTC, 0, T10s, 1, 0) If (ibsta And EERR) Then ErrMsg = "Unable to open Temp. Controller" & Chr(13) & "ibsta = &H" & _ Chr(13) & Hex(ibsta) & "iberr = " & iberr MsgBox ErrMsg, vbCritical, "Error" Exit Sub End If ilclr DevTC% End Sub

133

Sub GPIBCleanup(msg$, Dev%)

' After each GPIB call, the application checks whether the call ' succeeded. If an NI-488.2 call fails, the GPIB driver sets the ' corresponding bit in the global status variable. If the call ' failed, this procedure prints an error message, takes the device ' offline and exits.

'ErrorMnemonic = Array("EDVR", "ECIC", "ENOL", "EADR", "EARG", _ "ESAC", "EABO", "ENEB", "EDMA", "", _ "EOIP", "ECAP", "EFSO", "", "EBUS", _ "ESTB", "ESRQ", "", "", "", "ETAB")

'ErrMsg$ = msg$ & Chr(13) & "ibsta = &H" & Hex(ibsta) & Chr(13) _ & "iberr = " & iberr & " <" & ErrorMnemonic(iberr) & ">" 'MsgBox ErrMsg$, vbCritical, "Error" ilonl Dev%, 0

End Sub

Sub FindInstruments() InitializeSM InitializeSW InitializeTC

End Sub

*********************************************************************** frmMessage.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private Sub cmdClose_Click() Unload Me End Sub

Private Sub Form_Load() Me.Left = 3465 Me.Top = 1800 Me.Visible = True Me.pgbSearch.value = 5 DoEvents InitializeSM InitializeSW InitializeTC Me.lblGPIBSM.Caption = "GPIB Address = " & GPIBSM Me.lblGPIBSW.Caption = "GPIB Address = " & GPIBSW Me.lblGPIBTC.Caption = "GPIB Address = " & GPIBTC For i = 5 To 33

134 Me.pgbSearch.value = i DoEvents Wait 0.005 Next i SendSM "*IDN?", stat% If stat% = 0 Then ReadSM r$ Me.lblInstrment.Caption = "1. " & r$ Me.lblStatusSM.Caption = "Found" SendSM ":SYST:RSEN OFF", stat% DoEvents Else Me.lblStatusSM.Caption = "Not Found" End If

'******************************************** SendSW "*IDN?", stat% For i = 33 To 66 Me.pgbSearch.value = i DoEvents Wait 0.005 Next i If stat% = 0 Then ReadSW r$ Me.lblInstrment.Caption = lblInstrment.Caption & Chr(13) & "2. " & r$

Me.lblStatusSW.Caption = "Found" fMainForm.chkMidGND.Enabled = True For i = 0 To 9 fMainForm.TgB(i).Enabled = True Next i Else Me.lblStatusSW.Caption = "Not Found" fMainForm.chkMidGND.Enabled = False For i = 0 To 9 fMainForm.TgB(i).Enabled = False Next i End If '******************************************** SendTC "*IDN?", stat% For i = 66 To 100 Me.pgbSearch.value = i DoEvents Wait 0.005 Next i If stat% = 0 Then Me.lblInstrment.Caption = lblInstrment.Caption & Chr(13) & "3. " & ReadTC("*IDN?" & Chr(13)) Me.lblStatusTC.Caption = "Found" fMainForm.tbToolBar.Buttons.Item(16).Enabled = True fMainForm.tbToolBar.Buttons.Item(17).Enabled = True Else Me.lblStatusTC.Caption = "Not Found" fMainForm.tbToolBar.Buttons.Item(16).Enabled = False fMainForm.tbToolBar.Buttons.Item(17).Enabled = False End If Me.lblSearching.Visible = False

135 Me.pgbSearch.value = 100 DoEvents Me.cmdClose.Enabled = True End Sub

*********************************************************************** frmDocument.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Dim oBook As Excel.Workbook Dim oSheet As Excel.Worksheet Dim oSheet2 As Excel.Worksheet Dim oChart As Excel.Chart Dim oChart2 As Excel.Chart Dim NoG As Long Dim r2 As Long Dim c2% Dim TData(1 To 200, 1 To 2) As Single Private i As Double Private VV As Double Private II As Double

Private Sub chkGradiCheck_Click() If chkGradiCheck.value = 0 Then chkSaveTransient.Enabled = False Else chkSaveTransient.Enabled = True End If End Sub

Private Sub chkSweep_Click() If chkSweep.value = 1 Then txtNoCycle.Enabled = True txtNoTranCycle.Enabled = True Label22.Enabled = True Else txtNoCycle.Enabled = False txtNoTranCycle.Enabled = False Label22.Enabled = False End If End Sub

Private Sub cmbDescription_Click() txtCellNo = cmbDescription.ListIndex + 1 DescripChange End Sub

Private Sub cmbDescription_DropDown() DescripChange End Sub

Private Sub cmbDescription_KeyPress(KeyAscii As Integer)

136 If KeyAscii = 13 Then DescripChange End If End Sub

Private Sub cmbDescription_LostFocus() DescripChange End Sub Sub DescripChange() cmbDescription.List(txtCellNo - 1) = cmbDescription.Text cmbDescription.ListIndex = txtCellNo - 1

With oSheet If NoG > 0 Then ' If txtCellNo < cmbDescription.ListCount Then ' oChart.SeriesCollection(Val(txtCellNo.Text)).ChartType = xlXYScatterSmooth ' End If '.Cells(3, txtCellNo * 2).value = cmbDescription.List(txtCellNo- 1) End If End With End Sub

Private Sub cmdBrowsF_Click() On Error Resume Next With CommonDialog .DialogTitle = "Enter File name" .CancelError = True .Filter = "Excel File (*.xls)|*.xls" .FileName = txtFileName .Flags = cdlOFNOverwritePrompt .ShowSave txtFileName = .FileName Caption = .FileName Save End With End Sub

Private Sub cmdGColor_Click(Index As Integer)

CommonDialog.ShowColor oBook.Colors(Index + 25) = CommonDialog.Color cmdGColor(Index).BackColor = CommonDialog.Color Exit Sub With oChart.SeriesCollection(Index + 1) .Border.Color = CommonDialog.Color .MarkerBackgroundColor = CommonDialog.Color .MarkerForegroundColor = 0 .MarkerSize = 4 End With

End Sub

Private Sub cmdSave_Click() Save End Sub

137

Private Sub cmdSMCont_Click() frmSMCont.Visible = True End Sub

Private Sub Form_Activate() If Me.optMidGND = True Then fMainForm.chkMidGND = 1 Else fMainForm.chkMidGND = 0 End If fMainForm.opt4Wire = Me.opt4Wire fMainForm.opt2Wire = Me.opt2Wire End Sub

Private Sub Form_Initialize() Me.optMidGND.value = fMainForm.chkMidGND.value End Sub

Private Sub Form_Load() Dim Para(1 To 12, 1 To 1) As Single ' OLE1.CreateEmbed "", "excel.chart" Set oBook = OLE1.object Set oChart = oBook.Charts(1) Set oChart2 = oBook.Charts(2) Set oSheet = oBook.Worksheets(1) Set oSheet2 = oBook.Worksheets(2) c2% = 1 r2 = 1 cmbDescription.List(0) = "Cell No 1" cmbDescription.ListIndex = 0

For i = 0 To 19 cmdGColor(i).BackColor = oBook.Colors(i + 25) Next i

If IVTMode = False Then txtStartT.Enabled = False txtEndT.Enabled = False txtStepT.Enabled = False Else txtStartT.Enabled = True txtEndT.Enabled = True txtStepT.Enabled = True End If opt4Wire.value = fMainForm.opt4Wire.value Me.opt4Wire.value = fMainForm.opt4Wire.value Me.opt2Wire.value = fMainForm.opt2Wire.value

SetSetupPara 'this subprogram assign all parameter values from frmSetup DoEvents

Para(1, 1) = txtSize Para(2, 1) = txtStartV Para(3, 1) = txtEndV Para(4, 1) = txtStepV Para(5, 1) = txtCurrentlimit

138 Para(6, 1) = txtDelay Para(7, 1) = txtAvg Para(8, 1) = txtNoCycle Para(9, 1) = 0 Para(10, 1) = txtStartT Para(11, 1) = txtEndT Para(12, 1) = txtStepT

With oSheet .Cells(2, 3).value = txtFileName .Cells(3, 3).value = txtDescription .Cells(5, 3).value = Date .Cells(5, 4).value = Time .Range("C6", "C17").value = Para

End With

OLE1.Visible = True ' OLE1.Close 'Deactivate the OLE container ' Application.Assistant.Visible = True End Sub Private Sub Form_Resize() On Error Resume Next OLE1.Move 115, 320, Me.ScaleWidth - 200, Me.ScaleHeight - 500 freSet.Move 115, 315, Me.ScaleWidth - 200, Me.ScaleHeight - 500 tbsGtoS.Width = Me.ScaleWidth - 200 End Sub Sub FopenForPhotoIV(FileName As String) OLE1.CreateEmbed FileName, "excel.chart" Set oBook = OLE1.object Set oSheet = oBook.Worksheets(1)

With oSheet If Left(.Cells(1, 1).value, 39) <> "Viraj2005 Automated IVT Setup Data File" Then MsgBox "This is not a correct Viraj2005 IVT Curve file", vbOKOnly + vbInformation, "Invalied file format" Exit Sub End If Set oChart = oBook.Charts(1) CNo% = .Cells(4, 4).value lblChannelNo = CNo% frmSetup.TgB(CNo% - 1).value = 1 'frmSetup.TgB_Click CNo% - 1

End With For z% = 1 To NoG cmbDescription.List(z% - 1) = oSheet.Cells(3, 2 * z%).value Next z% cmbDescription.AddItem "Cell No " & LTrim(Str(NoG + 1))

End Sub

Sub Save() oSheet.Cells(4, 4).value = Val(lblChannelNo.Caption) If txtFileName = "" Then On Error GoTo ErrHandler

139 With CommonDialog .CancelError = True .Filter = "Excel File (*.xls)|*.xls" .DialogTitle = "Save IV Curve File" .Flags = cdlOFNOverwritePrompt .ShowSave If Len(.FileName) = 0 Then Exit Sub End If txtFileName = .FileName End With Caption = txtFileName End If On Error GoTo ErrHandler oBook.Windows.Item(1).Visible = True oBook.Windows.Item(1).WindowState = xlMaximized oBook.SaveCopyAs txtFileName

ErrHandler: Exit Sub End Sub

Sub SaveAs() On Error GoTo ErrHandler With CommonDialog .CancelError = True .Filter = "Excel File (*.xls)|*.xls" .DialogTitle = "Save IV Curve File As" .Flags = cdlOFNOverwritePrompt .ShowSave If Len(.FileName) = 0 Then Exit Sub End If txtFileName = .FileName End With oBook.SaveCopyAs txtFileName Caption = txtFileName

ErrHandler: Exit Sub End Sub

Sub GetIV(Temp As Single) Dim i As Single Dim SCIndex As Integer 'Series collection Index SCIndex = 1 test: SendSM "*RST", stat% If stat% <> 0 Then cho = MsgBox("KEITHLEY 2400 SourceMeter not found", vbRetryCancel + vbExclamation, "GPIB Address Error") If cho = 4 Then GoTo test Else Exit Sub End If End If

140

With oSheet NoG = .Cells(4, 3).value + 1 cn% = (NoG * 5) - 4 Rn% = 20 If NoG > 1 Then Set oRng1 = oSheet.Range("A7:E20") Set oRng2 = oSheet.Range(.Cells(7, cn%), .Cells(20, cn% + 4)) Call oRng1.Copy(Destination:=oRng2) End If If Temp > 0 Then If optDark = True Then .Cells(18, cn% + 1).value = Temp Else .Cells(18, cn% + 2).value = Temp End If Else .Cells(18, cn% + 1).value = " " .Cells(18, cn% + 2).value = " " End If

If NoG > 1 Then oChart.SeriesCollection.NewSeries SCIndex = oChart.SeriesCollection.Count oChart.SeriesCollection(SCIndex).Name = .Range(.Cells(18, cn% + 1), .Cells(19, cn% + 1)) End If End With With oChart .Axes(xlCategory).MinimumScale = txtStartV.Text .Axes(xlCategory).MaximumScale = txtEndV.Text End With iprot$ = ":SENS:CURR:PROT " & Str(txtCurrentlimit.Text / 1000) VLevel$ = ":SOUR:VOLT:LEV " & txtStartV.Text SDelay$ = ":SOUR:DEL " & txtDelay.Text ' Avg$ = ":SENS:AVER:COUN " & TxtAvg.Text SendSM ":SOUR:FUNC VOLT", stat% SendSM ":SOUR:VOLT:MODE FIXED", stat% SendSM ":SENS:FUNC 'CURR'", stat% SendSM iprot$, stat% SendSM VLevel$, stat% SendSM ":SENS:CURR:RANG:AUTO ON", stat% SendSM SDelay$, stat% ' SendSM Avg$, stat% ' SendSM ":SENS:AVER:STAT ON", stat% If opt4Wire.value = True Then SendSM ":SYST:RSEN ON", stat% Else SendSM ":SYST:RSEN OFF", stat% End If SendSM ":OUTPUT ON", stat%

StartV = Val(txtStartV) EndV = Val(txtEndV) StepV = Val(txtStepV) NoCycle% = CInt(Val(txtNoCycle))

141 c2% = 1

For NoSweep% = 1 To NoCycle% r2 = 1 If chkSweep.value = 1 Then oSheet2.Cells(r2, c2%).value = "time (s)" oSheet2.Cells(r2, c2% + 1).value = "Current(A)" oSheet2.Cells(r2, c2% + 2).value = "Bias Voltage (V)" End If r2 = r2 + 1

For i = StartV To EndV Step StepV t = Timer() ' VV = 0 ok = 0 SendSM ":SOUR:VOLT:LEV " & Str(i), stat% oSheet2.Cells(r2, c2% + 2).value = Str(i)

'********************* If Gradient Check ON *************************** If chkGradiCheck.value = 1 Then

While ok = 0 k = 1 II = 0 IOld = 0 n = 0

For j = 1 To txtAvg.Text '************* Check START/PAUSE/STOP Status************* With fMainForm If .tbToolBar.Buttons.Item(12).value = tbrUnpressed Then If .tbToolBar.Buttons.Item(13).value = tbrPressed Then ' .MousePointer = 0 While

.tbToolBar.Buttons.Item(13). value = tbrPressed DoEvents Wend End If If .tbToolBar.Buttons.Item(12).value = tbrUnpressed Then ' .MousePointer = 0 GoTo Finalize 'Exit Sub End If End If '.MousePointer = 11 End With

'*********************************************************

SendSM "read?", stat% ReadSM r$ TData(k, 1) = Timer() - t

142 INew = Val(Mid(r$, 15, 13)) TData(k, 2) = INew

If IOld < INew Then n = n + 1 If IOld > INew Then n = n - 1 II = II + INew IOld = INew DoEvents k = k + 1 Next j

If Val(txtNoTranCycle.Text) >= NoSweep% And chkSaveTransient.value = 1 Then k = k - 1 oSheet2.Range(oSheet2.Cells(r2, c2%), oSheet2.Cells(r2 + k - 1, c2% + 1)).value = TData r2 = r2 + k oChart2.SeriesCollection(1).XValues = oSheet2.Range(oSheet2.Cells(2, c2%), oSheet2.Cells(r2 + 1, c2%)) oChart2.SeriesCollection(1).Values = oSheet2.Range(oSheet2.Cells(2, c2% + 1), oSheet2.Cells(r2 + 1, c2% + 1)) DoEvents End If If Abs(n) < 4 Then ok = 1 Wend Else

'********************* If Gradient Check OFF ************************* II = 0 For j = 1 To Val(txtAvg.Text) '************* Check START/PAUSE/STOP Status************* With fMainForm If .tbToolBar.Buttons.Item(12).value = tbrUnpressed Then If .tbToolBar.Buttons.Item(13).value = tbrPressed Then ' .MousePointer = 0 While .tbToolBar.Buttons.Item(13).value = tbrPressed DoEvents Wend End If If .tbToolBar.Buttons.Item(12).value = tbrUnpressed Then ' .MousePointer = 0 GoTo Finalize 'Exit Sub End If End If '.MousePointer = 11 End With '********************************************************* SendSM "read?", stat% ReadSM r$ INew = Val(Mid(r$, 15, 13))

143 II = II + INew DoEvents Next j End If '****************************************************************

VV = Val(Mid(r$, 1, 13)) II = II / txtAvg.Text With oSheet .Cells(Rn%, cn%).value = VV If optDark.value = True Then .Cells(Rn%, cn% + 1).value = Abs(II) If chkSaveIwithSign.value = 1 Then .Cells(Rn%, cn% + 2).value = II End If DoEvents oChart.SeriesCollection(SCIndex).XValues= .Range(.Cells(20, cn%), .Cells(Rn%, cn%)) oChart.SeriesCollection(SCIndex).Values = .Range(.Cells(20, cn% + 1), .Cells(Rn%, cn% + 1)) Else 'oSheet.Cells(Rn%, cn% + 1).value = Abs(II) oSheet.Cells(Rn%, cn% + 4).value = Abs(II) DoEvents oChart.SeriesCollection(SCIndex).XValues = .Range(.Cells(20, cn%), .Cells(Rn%, cn%)) oChart.SeriesCollection(SCIndex).Values = .Range(.Cells(20, cn% + 2), .Cells(Rn%, cn% + 4)) End If End With DoEvents Rn% = Rn% + 1 Next i

TempStartV = StartV StartV = EndV EndV = TempStartV StepV = -StepV If chkSweep.value = 1 And chkSaveTransient.value = 1 Then c2% = c2% + 3 End If Next NoSweep%

Finalize: SendSM ":OUTPUT OFF", stat% cmbDescription.List(SCIndex) = "Cell No " & LTrim(Str(NoG + 1)) cmbDescription.ListIndex = SCIndex - 1 oSheet.Cells(4, 3).value = NoG oSheet.Cells(14, cn% + 2).value = Rn% - 20 If chkFindR.value = 1 Then Set oRng1 = oSheet.Range(oSheet.Cells(20, cn% + 3), oSheet.Cells(20, cn% + 3)) Set oRng2 = oSheet.Range(oSheet.Cells(20, cn% + 3), oSheet.Cells(Rn% - 2, cn% + 3)) Call oRng1.AutoFill(Destination:=oRng2) End If End Sub

144

Private Sub Form_Unload(Cancel As Integer) If txtFileName = "" Then cho = MsgBox("Do you want to save the changes on " & Me.Caption, vbYesNoCancel + vbQuestion, "Viraj2005IVT") If cho = 2 Then Cancel = 1 Exit Sub ElseIf cho = 6 Then Save End If Else Save End If End Sub

Private Sub freTS_Click() If IVTMode = False Then txtStartT.Enabled = False txtEndT.Enabled = False txtStepT.Enabled = False Else txtStartT.Enabled = True txtEndT.Enabled = True txtStepT.Enabled = True End If

End Sub

Private Sub Frame5_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single) freModeFig.Visible = False End Sub

Private Sub opt2Wire_Click() If opt2Wire.value = True Then SendSM ":SYST:RSEN OFF", stat% fMainForm.opt2Wire.value = True End If End Sub

Private Sub opt4Wire_Click() If opt4Wire.value = True Then SendSM ":SYST:RSEN ON", stat% fMainForm.opt4Wire.value = True End If End Sub

Private Sub optMidGND_Click() If optMidGND.value = True Then SendSW ":clos (@ 1!22)", stat% SendSW ":open (@ 1!21)", stat% fMainForm.chkMidGND.value = 1 End If

145

End Sub

Private Sub optMidGND_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single) freModeFig.Visible = True End Sub

Private Sub optSepGND_Click() If optMidGND.value = False Then SendSW ":clos (@ 1!21)", stat% SendSW ":open (@ 1!22)", stat% fMainForm.chkMidGND.value = 0 End If

End Sub

Private Sub optSepGND_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single) freModeFig.Visible = True End Sub

Private Sub tbsGtoS_Click() Select Case tbsGtoS.SelectedItem.Index Case 1 freSet.Visible = False oChart.Activate OLE1.Visible = True oChart.Axes(xlValue).ScaleType = xlLogarithmic Case 2 freSet.Visible = False oChart.Activate OLE1.Visible = True oChart.Axes(xlValue).ScaleType = xlLinear Case 3 freSet.Visible = False oChart2.Activate OLE1.Visible = True oChart2.Axes(xlValue).ScaleType = xlLinear Case 4 freSet.Visible = True OLE1.Visible = False End Select End Sub

Sub SetSetupPara() txtStartV = frmSetup.txtStartV txtStepV = frmSetup.txtStepV txtEndV = frmSetup.txtEndV txtNoCycle = frmSetup.txtNoCycle chkSweep = frmSetup.chkSweep tglAutoVLimits = frmSetup.tglAutoVLimits txtCurrentlimit = frmSetup.txtCurrentlimit txtDelay = frmSetup.txtDelay txtAvg = frmSetup.txtAvg txtStartT = frmSetup.txtStartT

146 txtStepT = frmSetup.txtStepT txtEndT = frmSetup.txtEndT optDark = frmSetup.optDark optPhoto = frmSetup.optPhoto optMidGND = frmSetup.optMidGND optSepGND = frmSetup.optSepGND End Sub

Private Sub txtAvg_Change() oSheet.Cells(12, 3) = Val(txtAvg) End Sub

Private Sub txtCurrentlimit_Change() If txtCurrentlimit <> "" Then If txtCurrentlimit > 10 Then cho = MsgBox("! WARNING ! Your Current Limit is grater than 10mA" & Chr(10) & cr & "Are you sure", vbExclamation + vbYesNo, "WARNING") If cho <> 6 Then txtCurrentlimit = 10 End If End If oSheet.Cells(10, 3) = Val(txtCurrentlimit) End If End Sub

Private Sub txtDelay_Change() oSheet.Cells(11, 3) = Val(txtDelay) End Sub

Private Sub txtDescription_Change() oSheet.Cells(3, 3) = Val(txtDescription) End Sub

Private Sub txtEndT_Change() oSheet.Cells(16, 3) = Val(txtEndT) End Sub

Private Sub txtEndV_Change() oSheet.Cells(8, 3) = Val(txtEndV) End Sub

Private Sub txtFilename_Change() oSheet.Cells(2, 3) = Val(txtFileName) End Sub

Private Sub txtNoCycle_Change() oSheet.Cells(13, 3) = Val(txtNoCycle) End Sub

Private Sub txtSize_Change() oSheet.Cells(6, 3) = Val(txtSize) End Sub

Private Sub txtStartT_Change() oSheet.Cells(17, 3) = Val(txtStepT) End Sub

147 Private Sub txtStartV_Change() oSheet.Cells(7, 3) = Val(txtStartV) End Sub

Private Sub txtStepT_Change() oSheet.Cells(8, 3) = Val(txtStepT) End Sub

Private Sub txtStepV_Change() oSheet.Cells(9, 3) = Val(txtStepV) End Sub

Sub FindVlimit() oSV = frmSetup.txtStartV oEV = frmSetup.txtEndV SendSM ":OUTPUT ON", stat%

SendSM ":SOUR:VOLT:LEV " & Str(i), stat% Wait 0.2 SendSM "read?", stat% ReadSM r$ ' VNew = Val(Mid(r$, 1, 13)) INew = Val(Mid(r$, 15, 13))

End Sub

*********************************************************************** frmMain.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Begin VB.Menu mnuFile Caption = "&File" Begin VB.Menu mnuFileNew Caption = "&New" Shortcut = ^N End Begin VB.Menu mnuFileOpen Caption = "&Open..." Shortcut = ^O End Begin VB.Menu mnuFileClose Caption = "&Close" End Begin VB.Menu mnuFileBar0 Caption = "-" End Begin VB.Menu mnuFileSave Caption = "&Save" End Begin VB.Menu mnuFileSaveAs Caption = "Save &As..." End Begin VB.Menu mnuFileSaveAll Caption = "Save A&ll"

148 End Begin VB.Menu mnuFileBar1 Caption = "-" End Begin VB.Menu mnuFileProperties Caption = "Propert&ies" End Begin VB.Menu mnuFileBar2 Caption = "-" End Begin VB.Menu mnuFilePageSetup Caption = "Page Set&up..." End Begin VB.Menu mnuFilePrintPreview Caption = "Print Pre&view" End Begin VB.Menu mnuFilePrint Caption = "&Print..." End Begin VB.Menu mnuFileBar3 Caption = "-" End Begin VB.Menu mnuFileSend Caption = "Sen&d..." End Begin VB.Menu mnuFileBar4 Caption = "-" End Begin VB.Menu mnuFileMRU Caption = "" Index = 1 Visible = 0 'False End Begin VB.Menu mnuFileMRU Caption = "" Index = 2 Visible = 0 'False End Begin VB.Menu mnuFileMRU Caption = "" Index = 3 Visible = 0 'False End Begin VB.Menu mnuFileBar5 Caption = "-" Visible = 0 'False End Begin VB.Menu mnuFileExit Caption = "E&xit" End End Begin VB.Menu mnuEdit Caption = "&Edit" Begin VB.Menu mnuEditUndo Caption = "&Undo" End Begin VB.Menu mnuEditBar0

149 Caption = "-" End Begin VB.Menu mnuEditCut Caption = "Cu&t" Shortcut = ^X End Begin VB.Menu mnuEditCopy Caption = "&Copy" Shortcut = ^C End Begin VB.Menu mnuEditPaste Caption = "&Paste" Shortcut = ^V End Begin VB.Menu mnuEditPasteSpecial Caption = "Paste &Special..." End End Begin VB.Menu mnuView Caption = "&View" Begin VB.Menu mnuViewToolbar Caption = "&Toolbar" Checked = -1 'True End Begin VB.Menu mnuViewStatusBar Caption = "Status &Bar" Checked = -1 'True End Begin VB.Menu mnuViewBar0 Caption = "-" End Begin VB.Menu mnuViewRefresh Caption = "&Refresh" End Begin VB.Menu mnuViewOptions Caption = "&Options..." End Begin VB.Menu mnubar2 Caption = "-" End Begin VB.Menu mnuSMController Caption = "Source &Meter Controller" End Begin VB.Menu mnuSWsystem Caption = "&Switch System" End Begin VB.Menu mnuTempController Caption = "&Temperature Controller" End End Begin VB.Menu mnuTools Caption = "&Tools" Begin VB.Menu mnuInitializeSM Caption = "Initialize Source &Meter" End Begin VB.Menu mnuInitializeSW Caption = "Initialize &Switch System"

150 End Begin VB.Menu mnuInitializeTC Caption = "Initialize &Temp. Controller" End Begin VB.Menu mnubar3 Caption = "-" End Begin VB.Menu mnuSetupScane Caption = "Setup Scan" Begin VB.Menu mnuIVT Caption = "IVT" End Begin VB.Menu mnuIV Caption = "IV" End End Begin VB.Menu mnubar6 Caption = "-" End Begin VB.Menu mnuGPIB Caption = "Change GPIB Address" Begin VB.Menu mnuGPIBSM Caption = "KEITHLEY 2400 Source Meter" End Begin VB.Menu mnuGPIBSW Caption = "KEITHLEY 7001 Switch System" End Begin VB.Menu mnuGPIBTC Caption = "SI 9620-1 Temp. Controller" End End End Begin VB.Menu mnuWindow Caption = "&Window" WindowList = -1 'True Begin VB.Menu mnuWindowNewWindow Caption = "&New Window" End Begin VB.Menu mnuWindowBar0 Caption = "-" End Begin VB.Menu mnuWindowCascade Caption = "&Cascade" End Begin VB.Menu mnuWindowTileHorizontal Caption = "Tile &Horizontal" End Begin VB.Menu mnuWindowTileVertical Caption = "Tile &Vertical" End Begin VB.Menu mnuWindowArrangeIcons Caption = "&Arrange Icons" End End Begin VB.Menu mnuHelp Caption = "&Help" Begin VB.Menu mnuHelpContents

151 Caption = "&Contents" End Begin VB.Menu mnuHelpSearchForHelpOn Caption = "&Search For Help On..." End Begin VB.Menu mnuHelpBar0 Caption = "-" End Begin VB.Menu mnuHelpAbout Caption = "&About " End End End Attribute VB_Name = "frmMain" Attribute VB_GlobalNameSpace = False Attribute VB_Creatable = False Attribute VB_PredeclaredId = True Attribute VB_Exposed = False Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Any) As Long Const EM_UNDO = &HC7 Private Declare Function OSWinHelp% Lib "user32" Alias "WinHelpA" (ByVal hwnd&, ByVal HelpFile$, ByVal wCommand%, dwData As Any) Dim Form(1 To 10) As frmDocument Dim TvstForm As frmTempVsTime Dim TvstDoc As frmTempVsTime Dim DFileName(1 To 10) As String Private cr As String Private NoChanal As Integer Dim Pause As Boolean

Private Sub chkMidGND_Click() On Error GoTo errorhandler If chkMidGND.value = 1 Then SendSW ":clos (@ 1!22)", stat% SendSW ":open (@ 1!21)", stat% Me.ActiveForm.optMidGND = 1 Else SendSW ":clos (@ 1!21)", stat% SendSW ":open (@ 1!22)", stat% Me.ActiveForm.optSepGND = 1 End If errorhandler: End Sub

Private Sub cmdSMControl_Click() frmSMCont.Show vbModal, Me End Sub

Private Sub cmdSwitch_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) If cmdSwitch.Top = 180 Then cmdSwitch.Top = 720 IVTMode = False Else

152 cmdSwitch.Top = 180 IVTMode = True End If

End Sub

Private Sub MDIForm_Load() Me.Left = GetSetting(App.Title, "Settings", "MainLeft", 1000) Me.Top = GetSetting(App.Title, "Settings", "MainTop", 1000) Me.Width = GetSetting(App.Title, "Settings", "MainWidth", 6500) Me.Height = GetSetting(App.Title, "Settings", "MainHeight", 6500) LoadNewDoc cr = Chr(13) IVTMode = True NoChanal = 0

End Sub

Private Sub LoadNewDoc() Static lDocumentCount As Long Dim frmD As frmDocument lDocumentCount = lDocumentCount + 1 Set frmD = New frmDocument frmD.Caption = "IV Curve Book " & lDocumentCount frmD.Width = 9480 frmD.Height = Me.Height - 2700 frmD.Show End Sub

Private Sub MDIForm_Unload(Cancel As Integer) Close All If Me.WindowState <> vbMinimized Then SaveSetting App.Title, "Settings", "MainLeft", Me.Left SaveSetting App.Title, "Settings", "MainTop", Me.Top SaveSetting App.Title, "Settings", "MainWidth", Me.Width SaveSetting App.Title, "Settings", "MainHeight", Me.Height End If End End Sub

Private Sub mnuGPIBSM_Click() X = InputBox("Enter New GPIB Address of KEITHLEY 2400 Source Meter", "Change GPIB Address", GPIBSM) If X > 0 And X < 25 Then GPIBSM = X SaveSetting App.Title, "Settings", "GPIBSM", GPIBSM End If End Sub

Private Sub mnuGPIBSW_Click() X = InputBox("Enter New GPIB Address of KEITHLEY 7001 Switch System", "Change GPIB Address", GPIBSW) If X > 0 And X < 25 Then GPIBSW = X SaveSetting App.Title, "Settings", "GPIBSW", GPIBSW End If

153 End Sub

Private Sub mnuGPIBTC_Click() X = InputBox("Enter New GPIB Address of SI 9620-1 Temp. Controller", "Change GPIB Address", GPIBTC) If X > 0 And X < 30 Then GPIBTC = X SaveSetting App.Title, "Settings", "GPIBTC", GPIBTC End If End Sub

Private Sub mnuSMController_Click() frmSMCont.Visible = True End Sub

Private Sub mnuSWsystem_Click() Keithley7001.Visible = True End Sub

Private Sub mnuTempController_Click() TempController.Visible = True End Sub

Private Sub opt2Wire_Click() On Error GoTo errorhandler If opt2Wire.value = True Then SendSM ":SYST:RSEN OFF", stat% Me.ActiveForm.opt2Wire = 1 End If errorhandler: End Sub

Private Sub opt4Wire_Click() On Error GoTo errorhandler If opt4Wire.value = True Then SendSM ":SYST:RSEN ON", stat% Me.ActiveForm.opt4Wire = 1 End If errorhandler: End Sub

Private Sub tbToolBar_ButtonClick(ByVal Button As MSComctlLib.Button) On Error Resume Next Select Case Button.Key Case "New" LoadNewDoc

Case "Open" mnuFileOpen_Click

Case "Save" mnuFileSave_Click

Case "Print" If Form(1).Visible = False Then MsgBox "aa" End If

154 Case "Initialize" frmMessage.Show

Case "Setup" frmSetup.Show vbModal, Me

Case "Options"

Case "Settings" frmOptions.Show vbModal, Me

Case "Start" If Pause = False Then RunScan Else Pause = False End If Case "Pause" If tbToolBar.Buttons.Item(13).value = tbrPressed Then Pause = True Else Pause = False End If Case "Stop" Button.value = tbrUnpressed TvstForm.cmdClose.Enabled = True Toolbar1.Enabled = True fMainForm.Frame2.Enabled = True Case "TempCont" TempController.Visible = True

Case "ShowT" If Button.value = tbrPressed Then txtlblT1.Visible = True txtT1.Visible = True txtlblT2.Visible = True txtT2.Visible = True txtlblH.Visible = True txth.Visible = True Set TvstDoc = New frmTempVsTime TvstDoc.Height = 6330 TvstDoc.Width = 8175 TvstDoc.Show tmrTemp.Enabled = True Else txtlblT1.Visible = False txtT1.Visible = False txtlblT2.Visible = False txtT2.Visible = False txtlblH.Visible = False txth.Visible = False tmrTemp.Enabled = False

End If End Select End Sub

155 Private Sub mnuHelpAbout_Click() frmAbout.Show vbModal, Me End Sub

Private Sub mnuHelpSearchForHelpOn_Click() Dim nRet As Integer

'if there is no helpfile for this project display a message to the user 'you can set the HelpFile for your application in the 'Project Properties dialog If Len(App.HelpFile) = 0 Then MsgBox "Unable to display Help Contents. There is no Help associated with this project.", vbInformation, Me.Caption Else On Error Resume Next nRet = OSWinHelp(Me.hwnd, App.HelpFile, 261, 0) If Err Then MsgBox Err.Description End If End If

End Sub

Private Sub mnuHelpContents_Click() Dim nRet As Integer

'if there is no helpfile for this project display a message to the user 'you can set the HelpFile for your application in the 'Project Properties dialog If Len(App.HelpFile) = 0 Then MsgBox "Unable to display Help Contents. There is no Help associated with this project.", vbInformation, Me.Caption Else On Error Resume Next nRet = OSWinHelp(Me.hwnd, App.HelpFile, 3, 0) If Err Then MsgBox Err.Description End If End If

End Sub

Private Sub mnuWindowArrangeIcons_Click() Me.Arrange vbArrangeIcons End Sub

Private Sub mnuWindowTileVertical_Click() Me.Arrange vbTileVertical End Sub

Private Sub mnuWindowTileHorizontal_Click() Me.Arrange vbTileHorizontal End Sub

156 Private Sub mnuWindowCascade_Click() Me.Arrange vbCascade End Sub

Private Sub mnuWindowNewWindow_Click() LoadNewDoc End Sub

Private Sub mnuViewOptions_Click() frmOptions.Show vbModal, Me End Sub

Private Sub mnuViewRefresh_Click() 'ToDo: Add 'mnuViewRefresh_Click' code. MsgBox "Add 'mnuViewRefresh_Click' code." End Sub

Private Sub mnuViewStatusBar_Click() mnuViewStatusBar.Checked = Not mnuViewStatusBar.Checked sbStatusBar.Visible = mnuViewStatusBar.Checked End Sub

Private Sub mnuViewToolbar_Click() mnuViewToolbar.Checked = Not mnuViewToolbar.Checked tbToolBar.Visible = mnuViewToolbar.Checked End Sub

Private Sub mnuEditPasteSpecial_Click() 'ToDo: Add 'mnuEditPasteSpecial_Click' code. MsgBox "Add 'mnuEditPasteSpecial_Click' code." End Sub

Private Sub mnuEditPaste_Click() On Error Resume Next ' ActiveForm.rtfText.SelRTF = Clipboard.GetText

End Sub

Private Sub mnuEditCopy_Click() On Error Resume Next ' Clipboard.SetText ActiveForm.rtfText.SelRTF

End Sub

Private Sub mnuEditCut_Click() On Error Resume Next ' Clipboard.SetText ActiveForm.rtfText.SelRTF ' ActiveForm.rtfText.SelText = vbNullString

End Sub

Private Sub mnuEditUndo_Click() 'ToDo: Add 'mnuEditUndo_Click' code. MsgBox "Add 'mnuEditUndo_Click' code." End Sub

Private Sub mnuFileExit_Click()

157 'unload the form Unload Me End Sub

Private Sub mnuFileSend_Click() 'ToDo: Add 'mnuFileSend_Click' code. MsgBox "Add 'mnuFileSend_Click' code." End Sub

Private Sub mnuFilePrint_Click() On Error Resume Next If ActiveForm Is Nothing Then Exit Sub

With dlgCommonDialog .DialogTitle = "Print" .CancelError = True .Flags = cdlPDReturnDC + cdlPDNoPageNums ' If ActiveForm.rtfText.SelLength = 0 Then ' .Flags = .Flags + cdlPDAllPages ' Else ' .Flags = .Flags + cdlPDSelection ' End If .ShowPrinter ' If err <> MSComDlg.cdlCancel Then ' ActiveForm.rtfText.SelPrint .hDC ' End If End With

End Sub

Private Sub mnuFilePrintPreview_Click() 'ToDo: Add 'mnuFilePrintPreview_Click' code. MsgBox "Add 'mnuFilePrintPreview_Click' code." End Sub

Private Sub mnuFilePageSetup_Click() On Error Resume Next With dlgCommonDialog .DialogTitle = "Page Setup" .CancelError = True .ShowPrinter End With

End Sub

Private Sub mnuFileSaveAll_Click() 'ToDo: Add 'mnuFileSaveAll_Click' code. MsgBox "Add 'mnuFileSaveAll_Click' code." End Sub

Private Sub mnuFileSaveAs_Click() If ActiveForm.Caption <> "Viraj2003 Multimeter" Then ActiveForm.SaveAs Else frmMultimeter.WindowState = 1 ActiveForm.SaveAs

158 frmMultimeter.WindowState = 0 End If End Sub

Private Sub mnuFileSave_Click() If ActiveForm.Caption <> "Viraj2003 Multimeter" Then ActiveForm.Save Else frmMultimeter.WindowState = 1 ActiveForm.Save frmMultimeter.WindowState = 0 End If End Sub

Private Sub mnuFileClose_Click() 'ToDo: Add 'mnuFileClose_Click' code. MsgBox "Add 'mnuFileClose_Click' code." End Sub

Private Sub mnuFileOpen_Click() OpenForPhotoIV End Sub

Private Sub mnuFileNew_Click() LoadNewDoc End Sub

Public Sub multioff() tbToolBar.Buttons.Item(5).value = tbrUnpressed End Sub

Private Sub tglIVt_GotFocus()

End Sub

Private Sub TgB_Click(Index As Integer) If TgB(Index).value = True Then lblLED(Index).BackColor = &HFF00& DoEvents For i = 0 To 9 If i - Index <> 0 Then TgB(i).value = False Next i CloseSW Index + 1, chkMidGND Else lblLED(Index).BackColor = &H0& CloseSW 0, chkMidGND End If

End Sub

Private Sub tmrTemp_Timer() txtT1.Text = Format(Mid(ReadTC("T" & cr), 2, 5), "000.0K") txtT2.Text = Format(Mid(ReadTC("t" & cr), 2, 5), "000.0K") txth.Text = Format(Mid(ReadTC("H" & cr), 2, 5), "000.0 W") TvstDoc.FillData Val(txtT1.Text), Val(txtT2.Text), False End Sub

159 Sub OpenNewDoc(n As Integer, DFileName() As String, mesaSize() As Single) NoChanal = n For i = 1 To n Set Form(i) = New frmDocument Form(i).txtSize = mesaSize(i) Form(i).txtFilename = DFileName(i) Form(i).Caption = Mid(DFileName(i), Len(DFileName(i)) - 4, 1) & " | " & DFileName(i) Form(i).Width = 9480 Form(i).Height = Me.Height - 2700 Form(i).Show Form(i).opt4Wire.value = True Form(i).lblChannelNo = Asc(Mid(DFileName(i), Len(DFileName(i)) - 4, 1)) - 64 Next i SaveProject For i = n To 2 Step -1 Form(i).WindowState = 1 DoEvents Next i

cho = MsgBox("Do you want START Scan now?" & Chr(10) & cr & "If you select you can Start it later using Start key", vbQuestion + vbYesNo, "START it Now?") If cho = 6 Then tbToolBar.Buttons.Item(12).value = tbrPressed 'Start button press RunScan End If

End Sub Sub OpenForPhotoIV() Dim fnames As Variant On Error GoTo ErrHandler

fnames = Application.GetOpenFilename("Excel Files (*.xls), *.xls", , , , MultiSelect:=True) NoChanal = UBound(fnames)

For i = 0 To 9 frmSetup.TgB(i).value = 0 Next i

Counter = 1 While Counter <= UBound(fnames) Set Form(Counter) = New frmDocument Form(Counter).Caption = fnames(Counter) Form(Counter).Height = Me.Height - 2700 Form(Counter).Width = 9480 Form(Counter).Show Form(Counter).FopenForPhotoIV (fnames(Counter))

Counter = Counter + 1 Wend ErrHandler:

End Sub Sub SaveProject()

160 For i = 1 To NoChanal Form(i).Save Next i End Sub

Sub RunScan()

'############################################################################ 'If Scan was setup and IVT mode is ON '############################################################################ Dim Temp As Single Frame2.Enabled = False If NoChanal > 0 And IVTMode = True Then Set TvstForm = New frmTempVsTime TvstForm.Height = 6330 TvstForm.Width = 8175 TvstForm.Top = 15 TvstForm.Left = 6045

TvstForm.Show TvstForm.Save txtlblT1.Visible = True txtT1.Visible = True txtlblT2.Visible = True txtT2.Visible = True txtlblH.Visible = True txth.Visible = True

Toolbar1.Enabled = False tbToolBar.Buttons.Item(17).value = tbrPressed

SendSM ":SYST:RSEN ON", stat%

For Temp = frmSetup.txtStartT To frmSetup.txtEndT Step frmSetup.txtStepT

TvstForm.OLE1.MousePointer = 11 TvstForm.SetTemp (Temp) 'To set the temp TvstForm.OLE1.MousePointer = 0 For Chanel = 1 To NoChanal

'************* Check START/PAUSE/STOP Status************* If tbToolBar.Buttons.Item(12).value = tbrUnpressed Then If tbToolBar.Buttons.Item(13).value = tbrPressed Then While tbToolBar.Buttons.Item(13).value = tbrPressed DoEvents Wend End If If tbToolBar.Buttons.Item(12).value = tbrUnpressed Then Exit Sub End If End If '********************************************************* CNo% = Asc(frmSetup.TabStrip1.Tabs(Chanel).Caption) - 64 CloseSW CNo%, frmSetup.optMidGND

161 PushChannel CNo% Form(Chanel).WindowState = 0

fMainForm.tmrTvst.Enabled = True Form(Chanel).OLE1.MousePointer = 11 Form(Chanel).GetIV Temp Form(Chanel).OLE1.MousePointer = 0 fMainForm.tmrTvst.Enabled = False

TvstForm.FillData Val(txtT1.Text), Val(txtT2.Text), True

Form(Chanel).Save Form(Chanel).WindowState = 1 Next Chanel

Next Temp TvstForm.Save TvstForm.cmdClose.Enabled = True tbToolBar.Buttons.Item(17).value = tbrUnpressed

'************* To find Heter ON/OFF and set it to OFF SendTC "S3000" & cr, stat% SendTC "X" & cr, stat% Wait 1 If Val(Mid(ReadTC("H" & cr), 2, 5)) > 0 Then SendTC "X" & cr, stat% End If '*************** SendSM ":SYST:RSEN OFF", stat% For Chanel = 1 To NoChanal Form(Chanel).WindowState = 0 Next Chanel

End If

'###################################################################### 'If Scan was setup and IV mode is ON '###################################################################### If NoChanal > 0 And IVTMode = False Then SendSM ":SYST:RSEN ON", stat% For Chanel = 1 To NoChanal '************* Check START/PAUSE/STOP Status************* If tbToolBar.Buttons.Item(12).value = tbrUnpressed Then If tbToolBar.Buttons.Item(13).value = tbrPressed Then While tbToolBar.Buttons.Item(13).value = tbrPressed DoEvents Wend End If If tbToolBar.Buttons.Item(12).value = tbrUnpressed Then Exit Sub End If End If '*********************************************************

CNo% = Asc(frmSetup.TabStrip1.Tabs(Chanel).Caption) - 64 CloseSW CNo%, frmSetup.optMidGND PushChannel CNo%

162

Form(Chanel).WindowState = 0

Form(Chanel).OLE1.MousePointer = 11 Form(Chanel).GetIV 0 Form(Chanel).OLE1.MousePointer = 0

Form(Chanel).Save Form(Chanel).WindowState = 1 'MsgBox CNo% Next Chanel SendSM ":SYST:RSEN OFF", stat% For Chanel = 1 To NoChanal Form(Chanel).WindowState = 0 Next Chanel

End If

'###################################################################### 'If Scan was not setup (Normal IV curve Mode) '###################################################################### If NoChanal = 0 Then Me.ActiveForm.OLE1.MousePointer = 11 Me.ActiveForm.GetIV 0 Me.ActiveForm.OLE1.MousePointer = 0 End If tbToolBar.Buttons.Item(12).value = tbrUnpressed SendSM ":OUTPUT OFF", stat% Frame2.Enabled = True

End Sub Sub UpdateTemp(T1 As Single, T2 As Single, H As Single) txtT1.Text = Format(T1, "000.0K") txtT2.Text = Format(T2, "000.0K") txth.Text = Format(H, "000.0 W") End Sub

Private Sub tmrTvst_Timer() txtT1.Text = Format(Mid(ReadTC("T" & cr), 2, 5), "000.0K") txtT2.Text = Format(Mid(ReadTC("t" & cr), 2, 5), "000.0K") txth.Text = Format(Mid(ReadTC("H" & cr), 2, 5), "000.0 W") TvstForm.FillData Val(txtT1.Text), Val(txtT2.Text), False End Sub Sub PushChannel(i As Integer) TgB(i - 1).value = True lblLED(i - 1).BackColor = &HFF00& For j = 0 To 9 If j - (i - 1) <> 0 Then TgB(j).value = False lblLED(j).BackColor = &H0& End If Next j ' CloseSW Index + 1, chkMidGND DoEvents End Sub

163

***********************************************************************frmSetup .frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Dim FileName(1 To 10) As String Dim mesaSize(1 To 10) As Single

Private Sub chkSweep_Click() If chkSweep.value = 1 Then txtNoCycle.Enabled = True Else txtNoCycle.Enabled = False End If End Sub

Private Sub cmdBrows_Click() On Error Resume Next With CommonDialog1 .DialogTitle = "Enter New Project Name" .CancelError = True .Filter = "All File (*.*)|*.*" .Flags = cdlOFNOverwritePrompt .ShowSave txtProjectName.Text = .FileName End With

If Right(txtProjectName.Text, 4) = ".xls" Then txtProjectName.Text = Left(txtProjectName.Text, Len(txtProjectName.Text) - 6) End If

For i = 1 To TabStrip1.Tabs.Count FileName(i) = txtProjectName.Text & "_" & TabStrip1.Tabs(i).Caption & ".xls" Next i cmdStartNewScan.Enabled = True TabStrip1_Click

End Sub

Private Sub cmdBrowsF_Click() On Error Resume Next With CommonDialog1 .DialogTitle = "Measa File name" .CancelError = True .Filter = "Excel File (*.xls)|*.xls" .FileName = FileName(TabStrip1.SelectedItem.Index) .Flags = cdlOFNOverwritePrompt .ShowSave .InitDir = FileName(TabStrip1.SelectedItem.Index) FileName(TabStrip1.SelectedItem.Index) = .FileName TabStrip1_Click End With End Sub

164

Private Sub cmdClose_Click() Me.Visible = False End Sub

Private Sub cmdGetSett_Click() ReadFormData Me, App.Path & "\Settings.dat" txtProjectName = "" End Sub

Private Sub cmdSaveSett_Click() SaveFormData Me, App.Path & "\Settings.dat" End Sub

Private Sub cmdSM_Click() frmSMCont.Frame3.Enabled = True frmSMCont.Show vbModal, Me End Sub

Private Sub cmdStartNewScan_Click() Me.Visible = False DoEvents If optExcelFile.value = True Then fMainForm.OpenNewDoc TabStrip1.Tabs.Count, FileName(), mesaSize() Else frmDataCollecting.Visible = True frmDataCollecting.IVFNames TabStrip1.Tabs.Count, FileName(), mesaSize()

End If End Sub

Private Sub Form_Activate() Me.opt4Wire.value = fMainForm.opt4Wire.value Me.opt2Wire.value = fMainForm.opt2Wire.value If fMainForm.chkMidGND.value = 1 Then Me.optMidGND.value = True Me.optSepGND.value = False Else Me.optMidGND.value = False Me.optSepGND.value = True End If End Sub

Private Sub Form_Load() For i = 1 To 10 mesaSize(i) = 1 Next i ReadFormData Me, App.Path & "\Settings.dat" txtProjectName = "" End Sub

Private Sub Form_Unload(Cancel As Integer) SaveFormData Me, App.Path & "\Settings.dat" End Sub

Private Sub Frame5_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)

165 freModeFig.Visible = False End Sub

Private Sub opt2Wire_Click() If opt2Wire.value = True Then SendSM ":SYST:RSEN OFF", stat% fMainForm.opt2Wire.value = True End If End Sub

Private Sub opt4Wire_Click() If opt4Wire.value = True Then SendSM ":SYST:RSEN ON", stat% fMainForm.opt4Wire.value = True End If End Sub

Private Sub optMidGND_Click() If optMidGND.value = True Then SendSW ":clos (@ 1!22)", stat% SendSW ":open (@ 1!21)", stat% fMainForm.chkMidGND.value = 1 End If

End Sub

Private Sub optMidGND_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single) freModeFig.Visible = True End Sub

Private Sub optSepGND_Click() If optMidGND.value = False Then SendSW ":clos (@ 1!21)", stat% SendSW ":open (@ 1!22)", stat% fMainForm.chkMidGND.value = 0 End If End Sub

Private Sub optSepGND_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single) freModeFig.Visible = True End Sub

Private Sub optSize_Click(Index As Integer) mesaSize(TabStrip1.SelectedItem.Index) = (400 + (200 * Index)) ^ 2 / 1000000 txtSize = mesaSize(TabStrip1.SelectedItem.Index) End Sub

Private Sub TabStrip1_Click() If Len(FileName(TabStrip1.SelectedItem.Index)) > 65 Then txtFilename.Text = "..." & Right(FileName(TabStrip1.SelectedItem.Index), 65) Else txtFilename.Text = FileName(TabStrip1.SelectedItem.Index) End If

166 txtSize = mesaSize(TabStrip1.SelectedItem.Index) End Sub

Sub TgB_Click(Index As Integer) If TgB(Index).value = True Then lblLED(Index).BackColor = &HFF00& TabStrip1.Tabs.Add , , TgB(Index).Caption For i = 1 To TabStrip1.Tabs.Count FileName(i) = txtProjectName.Text & "_" & TabStrip1.Tabs(i).Caption & ".xls" Next i Else lblLED(Index).BackColor = &H0& For i = 1 To TabStrip1.Tabs.Count If TabStrip1.Tabs.Item(i).Caption = TgB(Index).Caption Then TabStrip1.Tabs.Remove i FileName(i) = "" Exit For End If Next i End If

End Sub

Private Sub txtCurrentlimit_Change() If txtCurrentLimit <> "" Then If txtCurrentLimit > 10 Then cho = MsgBox("! WARNING ! Your Current Limit is grater than 10mA" & Chr(10) & cr & "Are you sure", vbExclamation + vbYesNo, "WARNING") If cho <> 6 Then txtCurrentLimit = 10 End If End If End If End Sub

Private Sub txtd_Change() txtSize = Format(4 * Atn(1) * (Val(txtd) / 2) ^ 2 / 1000000, "0.0000") End Sub

Private Sub txth_Change() txtSize = Val(txth) * Val(txtw) / 1000000 End Sub

Private Sub txtProjectName_Change() If txtProjectName.Text <> "" Then cmdStartNewScan.Enabled = True TabStrip1_Click Else cmdStartNewScan.Enabled = False End If End Sub

Private Sub txtSize_Change() mesaSize(TabStrip1.SelectedItem.Index) = Val(txtSize) End Sub

167

Private Sub txtw_Change() txtSize = Val(txth) * Val(txtw) / 1000000 End Sub

********************************************************************** frmSMCon.frm ********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private Sub cmdClose_Click() ' SendSM ":OUTPUT OFF", stat% SetV = chkSetVLimits SV = Val(txtVStart) EV = Val(txtVEnd) Unload Me If frmSetup.Visible And SetV = 1 Then frmSetup.txtStartV = SV frmSetup.txtEndV = EV ElseIf SetV = 1 Then fMainForm.ActiveForm.txtStartV = SV fMainForm.ActiveForm.txtEndV = EV End If End Sub

Private Sub cmdOutPutOnOff_Click() If cmdOutPutOnOff.Caption = "OutPut ON" Then cmdOutPutOnOff.Caption = "OutPut OFF" lblONOffLed.BackColor = &HFF& SendSM ":OUTPUT ON", stat% Timer1.Enabled = True Else cmdOutPutOnOff.Caption = "OutPut ON" lblONOffLed.BackColor = &O0& SendSM ":OUTPUT OFF", stat% lblV.Caption = Format(0, "#0.00000") lblI.Caption = Format(0, "###0.00000") Timer1.Enabled = False End If

End Sub

Private Sub cmdVset_Click() VLevel$ = ":SOUR:VOLT:LEV " & Val(txtVset) SendSM VLevel$, stat% End Sub

Private Sub Form_Load() SetLimits = False SendSM ":OUTPUT OFF", stat% SendSM ":SOUR:FUNC VOLT", stat% SendSM ":SOUR:VOLT:MODE FIXED", stat% SendSM ":SOUR:VOLT:RANG:AUTO ON", stat%

168 SendSM ":SENS:FUNC 'CURR'", stat% SendSM ":SENS:CURR:RANG:AUTO ON", stat% SendSM ":SOUR:DEL 0.1", stat% SendSM ":SOUR:VOLT:LEV 0.0", stat% iprot$ = ":SENS:CURR:PROT " & Str(txtCurrentLimit.Text / 1000) SendSM iprot$, stat% End Sub

Private Sub optFindV_Click() If cmdOutPutOnOff.Caption = "OutPut ON" Then cmdOutPutOnOff_Click End If SendSM ":OUTPUT ON", stat% ILimit = Val(txtCurrentLimit.Text) iprot$ = ":SENS:CURR:PROT " & Str(ILimit / 1000) SendSM iprot$, stat%

i = 0 Do VLevel$ = ":SOUR:VOLT:LEV " & Str(i) SendSM VLevel$, stat% i = i + 0.1 SendSM "read?", stat% ReadSM r$ Curr = Val(Mid(r$, 15, 13)) * 1000 If Curr > Val(txtCurrentLimit.Text) * 98 / 100 Then Exit Do End If txtVEnd = i If sldVset.Max < i * 100 Then sldVset.Max = i * 100 sldVset.TickFrequency = (sldVset.Max - sldVset.Min) / 100 End If sldVset.value = i * 100 DoEvents Loop While i < 20 And optFindV.value = True sldVset.Max = i * 100 '******************************************* i = 0 Do VLevel$ = ":SOUR:VOLT:LEV " & Str(i) SendSM VLevel$, stat% i = i - 0.1 SendSM "read?", stat% ReadSM r$ Curr = Val(Mid(r$, 15, 13)) * 1000 If Curr < -Val(txtCurrentLimit.Text) * 98 / 100 Then Exit Do End If txtVStart = i If sldVset.Min > i * 100 Then sldVset.Min = i * 100 sldVset.TickFrequency = (sldVset.Max - sldVset.Min) / 100 End If sldVset.value = i * 100

169 DoEvents Loop While i > -20 And optFindV.value = True sldVset.Min = i * 100 SendSM ":SOUR:VOLT:LEV 0.0", stat% sldVset.value = 0 optFindV.value = False End Sub

Private Sub optMidGND_Click() If optMidGND.value = True Then InitializeSW SendSW ":clos (@ 1!22)", stat% SendSW ":open (@ 1!21)", stat% fMainForm.chkMidGND.value = 1 End If End Sub

Private Sub optSepGND_Click() If optSepGND.value = True Then InitializeSW SendSW ":clos (@ 1!21)", stat% SendSW ":open (@ 1!22)", stat% fMainForm.chkMidGND.value = 0

End If End Sub

Private Sub optStop_Click() optStop.value = False End Sub

Private Sub sldVset_Change() VLevel$ = ":SOUR:VOLT:LEV " & sldVset.value / 100 SendSM VLevel$, stat% End Sub

Private Sub TgB_Click(Index As Integer) InitializeSW If TgB(Index).value = True Then lblLED(Index).BackColor = &HFF00& fMainForm.PushChannel Index + 1 DoEvents

For i = 0 To 9 If i - Index <> 0 Then TgB(i).value = False Next i CloseSW Index + 1, optMidGND Else lblLED(Index).BackColor = &H0& CloseSW 0, optMidGND End If End Sub

Private Sub Timer1_Timer() SendSM "read?", stat% ReadSM r$ lblV.Caption = Format(Val(Mid(r$, 1, 13)), "#0.00000")

170 lblI.Caption = Format(Val(Mid(r$, 15, 13)) * 1000000, "###0.00000") End Sub

Private Sub txtCurrentlimit_Change() If txtCurrentLimit <> "" Then If txtCurrentLimit > 10 Then cho = MsgBox("! WARNING ! Your Current Limit is grater than 10mA It may be harmfull for your divice" & Chr(10) & cr & "Are you sure ?", vbExclamation + vbYesNo, "WARNING") If cho <> 6 Then txtCurrentLimit = 10 End If End If ILimit = Val(txtCurrentLimit.Text) iprot$ = ":SENS:CURR:PROT " & Str(ILimit / 1000) SendSM iprot$, stat% End If

End Sub

Private Sub txtVEnd_Change() If Val(txtVEnd) > sldVset.Min / 100 And Val(txtVEnd) < 20 Then sldVset.Max = Val(txtVEnd) * 100 sldVset.TickFrequency = (sldVset.Max - sldVset.Min) / 100 End If End Sub

Private Sub txtVStart_Change() If Val(txtVStart) < sldVset.Max / 100 And Val(txtVStart) > -20 Then sldVset.Min = Val(txtVStart) * 100 sldVset.TickFrequency = (sldVset.Max - sldVset.Min) / 100 End If End Sub

*********************************************************************** frmTempvsTime.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Dim oBook As Excel.Workbook Dim oSheet As Excel.Worksheet Dim oChart As Excel.Chart Dim StartTime Dim FR% Dim LT1, LT2 As Single

Private Sub cmdClose_Click() Unload Me End Sub

171 Private Sub cmdMaximize_Click() Me.WindowState = 2 End Sub

Private Sub cmdMinimize_Click() Me.WindowState = 1 End Sub

Private Sub cmdNormal_Click() Me.WindowState = 0 End Sub

Private Sub cmdSaveAs_Click() SaveAs End Sub

Private Sub Form_Load() ' OLE1.CreateEmbed "", "excel.chart" Set oBook = OLE1.object Set oChart = oBook.Charts(1) Set oSheet = oBook.Worksheets(1) StartTime = Time() Exit Sub oSheet.Cells.Clear oChart.ChartType = xlXYScatterLines oChart.SetSourceData oSheet.Range("A13:B114"), xlColumns With oChart .HasTitle = True .ChartTitle.Text = "IV Curve of the Sample" .HasLegend = True .Legend.Interior.ColorIndex = xlNone .Legend.Border.LineStyle = xlNone .Legend.Font.Size = 10 .Legend.Left = 1 .Legend.Top = 20 .Axes(xlCategory, xlPrimary).HasTitle = True .Axes(xlCategory, xlPrimary).AxisTitle.Characters.Text = "Voltage (V)" .Axes(xlValue, xlPrimary).HasTitle = True .Axes(xlValue, xlPrimary).AxisTitle.Characters.Text = "Current Density (A/m²)" End With With oChart.Axes(xlValue) .HasMajorGridlines = False .HasMinorGridlines = False .MajorTickMark = xlInside .MinorTickMark = xlNone .TickLabelPosition = xlNextToAxis ' .TickLabels.NumberFormat = "0.00" .TickLabels.Font.Size = 10 .ScaleType = xlLogarithmic End With With oChart.Axes(xlCategory) .HasMajorGridlines = False .HasMinorGridlines = False .MajorTickMark = xlInside .MinorTickMark = xlNone .TickLabelPosition = xlNextToAxis

172 ' .TickLabels.NumberFormat = "0.00" .TickLabels.Font.Size = 10 End With

oChart.PlotArea.Interior.ColorIndex = xlNone

OLE1.Visible = True ' OLE1.Close 'Deactivate the OLE container Application.Assistant.Visible = True

End Sub

Private Sub Form_Resize() On Error Resume Next OLE1.Move 200, 200, Me.ScaleWidth - 400, Me.ScaleHeight - 1000 Frame1.Top = Me.ScaleHeight - 800 Frame1.Left = ((Me.ScaleWidth - 4320) / 2) End Sub

Sub Save() Dim sFile As String On Error GoTo ErrHandler sFile = frmSetup.txtProjectName & "_TempVsTime.xls" oBook.Windows.Item(1).Visible = True oBook.Windows.Item(1).WindowState = xlMaximized oBook.SaveCopyAs sFile Caption = "T vs. t |" & sFile cmdClose.Enabled = False ErrHandler: Exit Sub End Sub

Sub SaveAs() Dim sFile As String On Error GoTo ErrHandler With CommonDialog .CancelError = True .Filter = "Excel File (*.xls)|*.xls" .DialogTitle = "Save IV Curve File As" .Flags = cdlOFNOverwritePrompt .ShowSave If Len(.filename) = 0 Then Exit Sub End If sFile = .filename End With oBook.Windows.Item(1).Visible = True oBook.Windows.Item(1).WindowState = xlMaximized oBook.SaveCopyAs sFile Caption = "T vs. t |" & sFile

ErrHandler: Exit Sub End Sub

Sub FillData(T1 As Single, T2 As Single, IVPoint As Boolean) With oSheet

173 If Abs(T1 - LT1) > frmOptions.txtTempTol Or Abs(T2 - LT2) > frmOptions.txtTempTol Then RW% = .Cells(14, 3).value + 20 .Cells(14, 3).value = RW% - 19 If RW% > 20 Then LT1 = T1 LT2 = T2 End If Else RW% = .Cells(14, 3).value + 19 End If .Cells(RW%, 1) = Time - StartTime .Cells(RW%, 2) = T1 .Cells(RW%, 3) = T2 oChart.SeriesCollection(1).XValues = .Range("A20:A" & RW%) oChart.SeriesCollection(1).Values = .Range("B20:B" & RW%) oChart.SeriesCollection(2).XValues = .Range("A20:A" & RW%) oChart.SeriesCollection(2).Values = .Range("C20:C" & RW%) If IVPoint = True Then If FR% = 0 Then FR% = RW% .Cells(RW%, 4) = T2 + 2 * a oChart.SeriesCollection(3).XValues = .Range("A" & FR% & ":A" & RW%) oChart.SeriesCollection(3).Values = .Range("D" & FR% & ":D" & RW%) End If End With End Sub

Sub OldSetTemp(t As Single) Dim T1 As Single Dim T2 As Single Dim H As Single fMainForm.tmrTemp.Enabled = False cr = Chr(13) '************* To find Heter ON/OFF and set it to ON SendTC "S3000" & cr, stat% SendTC "X" & cr, stat% Wait 1 If Val(Mid(ReadTC("H" & cr), 2, 5)) = 0 Then SendTC "X" & cr, stat% End If SendTC "S100" & cr, stat%

'*************** SendTC "S" & t * 10 & cr, stat% T1 = Val(Mid(ReadTC("T" & cr), 2, 5)) T2 = Val(Mid(ReadTC("t" & cr), 2, 5)) H = Val(Mid(ReadTC("H" & cr), 2, 5)) fMainForm.UpdateTemp T1, T2, H

TSet = t While Abs(T2 - t) > frmOptions.txtTempTol While Abs(T1 - TSet) > Val(frmOptions.txtTempTol) '************* Check START/PAUSE/STOP Status************* With fMainForm If .tbToolBar.Buttons.Item(12).value = tbrUnpressed Then If .tbToolBar.Buttons.Item(13).value = tbrPressed Then '.MousePointer = 0

174 While .tbToolBar.Buttons.Item(13).value = tbrPressed DoEvents Wend End If If .tbToolBar.Buttons.Item(12).value = tbrUnpressed Then '.MousePointer = 0 Exit Sub End If End If '.MousePointer = 11 End With '********************************************************* Wait frmOptions.txtDelayT T1 = Val(Mid(ReadTC("T" & cr), 2, 5)) T2 = Val(Mid(ReadTC("t" & cr), 2, 5)) H = Val(Mid(ReadTC("H" & cr), 2, 5)) fMainForm.UpdateTemp T1, T2, H FillData T1, T2, False DoEvents Wend TSet = Val(Mid(ReadTC("S" & cr), 2, 5)) - (frmOptions.txtTempTol / 2) Wait 2 SendTC "S" & TSet * 10 & cr, stat% Wend FillData T1, T2, True End Sub

Sub SetTemp(t As Single) Dim T1 As Single Dim T2 As Single Dim H As Single fMainForm.tmrTemp.Enabled = False cr = Chr(13) Dim GCount As Integer

'************* To find Heter ON/OFF and set it to ON SendTC "S3000" & cr, stat% SendTC "X" & cr, stat% Wait 1 If Val(Mid(ReadTC("H" & cr), 2, 5)) = 0 Then SendTC "X" & cr, stat% End If SendTC "S100" & cr, stat%

'*************** SendTC "S" & t * 10 & cr, stat% T1 = Val(Mid(ReadTC("T" & cr), 2, 5)) T2 = Val(Mid(ReadTC("t" & cr), 2, 5)) H = Val(Mid(ReadTC("H" & cr), 2, 5)) fMainForm.UpdateTemp T1, T2, H

n% = 0 GCount = 0 While GCount < 20 / frmOptions.txtDelayT And n% < (1000 / frmOptions.txtDelayT) n = n + 1 '************* Check START/PAUSE/STOP Status*************

175 With fMainForm If .tbToolBar.Buttons.Item(12).value = tbrUnpressed Then If .tbToolBar.Buttons.Item(13).value = tbrPressed Then '.MousePointer = 0 While .tbToolBar.Buttons.Item(13).value = tbrPressed DoEvents Wend End If If .tbToolBar.Buttons.Item(12).value = tbrUnpressed Then '.MousePointer = 0 Exit Sub End If End If '.MousePointer = 11 End With '********************************************************* Wait frmOptions.txtDelayT T1 = Val(Mid(ReadTC("T" & cr), 2, 5)) T2 = Val(Mid(ReadTC("t" & cr), 2, 5)) H = Val(Mid(ReadTC("H" & cr), 2, 5)) fMainForm.UpdateTemp T1, T2, H FillData T1, T2, False DoEvents

If Abs(T1 - t) <= Val(frmOptions.txtTempTol) Then GCount = GCount + 1 End If Wend FillData T1, T2, True End Sub

*********************************************************************** TempController.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private cr As String

Private Sub cmdApply_Click() SendTC "S" & txtSetPoint.Text * 10 & cr, stat%

txtSetPoint.Text = Format(Mid(ReadTC("S" & cr), 2, 5), "000.0") txtProTerm.Text = Mid(ReadTC("P" & cr), 2, 2) txtIntTerm.Text = Mid(ReadTC("I" & cr), 2, 2) txtDerTerm.Text = Mid(ReadTC("D" & cr), 2, 2) End Sub

Private Sub cmdExit_Click() Timer1.Enabled = False Unload Me End Sub

Private Sub cmdHeater_Click()

176 SendTC "X" & cr, stat% If lblLED.BackColor = &H0& Then lblLED.BackColor = &HFF00& Else lblLED.BackColor = &H0& End If MousePointer = 11 Sleep 1000 If Val(Mid(ReadTC("H" & cr), 2, 5)) > 0 Then lblLED.BackColor = &HFF00& End If MousePointer = 0

End Sub

Private Sub Form_Load() cr = Chr(13) txtSetPoint.Text = Format(Mid(ReadTC("S" & cr), 2, 5), "000.0") txtProTerm.Text = Mid(ReadTC("P" & cr), 2, 2) txtIntTerm.Text = Mid(ReadTC("I" & cr), 2, 2) txtDerTerm.Text = Mid(ReadTC("D" & cr), 2, 2) Timer1.Enabled = True End Sub

Private Sub Form_Unload(Cancel As Integer) Timer1.Enabled = False ' ilonl Dev%, 0 End Sub

Private Sub Timer1_Timer() lblT1.Caption = Format(Mid(ReadTC("T" & cr), 2, 5), "000.0 K") lblT2.Caption = Format(Mid(ReadTC("t" & cr), 2, 5), "000.0 K") lblH.Caption = Format(Mid(ReadTC("H" & cr), 2, 5), "000.0 W") End Sub

*********************************************************************** Keithley7001.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private Sub optMidGND_Click() If optMidGND.value = True Then InitializeSW SendSW ":clos (@ 1!22)", stat% SendSW ":open (@ 1!21)", stat% End If End Sub

Private Sub optSepGND_Click() If optSepGND.value = True Then InitializeSW SendSW ":clos (@ 1!21)", stat% SendSW ":open (@ 1!22)", stat% End If

177 End Sub

Private Sub TgB_Click(Index As Integer) InitializeSW If TgB(Index).value = True Then lblLED(Index).BackColor = &HFF00& DoEvents For i = 0 To 9 If i - Index <> 0 Then TgB(i).value = False Next i CloseSW Index + 1, optMidGND Else lblLED(Index).BackColor = &H0& CloseSW 0, optMidGND End If End Sub

*********************************************************************** frmDataCollecting.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Dim DFileName(1 To 10) As String Dim mesaSize(1 To 10) As Single Dim NoChannel As Integer Dim fNo1 As Integer Dim fNo2 As Integer Dim tStart As Variant

Private Sub Form_Load() optPause.value = False optPause.Enabled = False optStop.Enabled = False optPlay.value = False

End Sub

Private Sub optPlay_Click() If optPause.Enabled = False And optStop.Enabled = False Then optPause.Enabled = True optStop.Enabled = True End If fNo1 = FreeFile() Open Left(DFileName(1), Len(DFileName(1) - 2)) & "_" & "Tvst" & ".txt" For Output As #fNo1

SetSourceMeter tStart = Timer() Dim Temp As Single pbrOP.value = 2

For Temp = frmSetup.txtStartT To frmSetup.txtEndT Step frmSetup.txtStepT lblStatus.Caption = "Waiting for Temp. " & Temp SetTemp (Temp) 'To set the temp

178 For Channel = 1 To NoChannel GetIV Channel, Temp pbrOP.value = pbrOP.value + Int(((1 / NoChannel) * (frmSetup.txtStepT / Abs(frmSetup.txtEndT - frmSetup.txtStartT)))) Close #fNo1 fNo1 = FreeFile() Open Left(DFileName(1), Len(DFileName(1) - 2)) & "_" & "Tvst" & ".txt" For Append As #fNo1 Next Channel

pbrOP.value = Int(Abs(Temp - frmSetup.txtStartT) * 100 / Abs(frmSetup.txtEndT - frmSetup.txtStartT))

Next Temp

Close fNo1 End Sub

Private Sub optStop_Click() optStop.value = False End Sub

Sub IVFNames(n As Integer, FName() As String, MSize() As Single) NoChannel = n For i = 1 To n DFileName(i) = Left(FName(i), Len(FName(i)) - 3) mesaSize(i) = MSize(i) Next i End Sub

Sub SetTemp(t As Single) Dim T1 As Single Dim T2 As Single Dim H As Single fMainForm.tmrTemp.Enabled = False cr = Chr(13) Dim GCount As Integer

'*************** SendTC "S" & t * 10 & cr, stat% T1 = Val(Mid(ReadTC("T" & cr), 2, 5)) T2 = Val(Mid(ReadTC("t" & cr), 2, 5)) H = Val(Mid(ReadTC("H" & cr), 2, 5)) fMainForm.UpdateTemp T1, T2, H

n% = 0 GCount = 0

179 While GCount < 20 / frmOptions.txtDelayT And n% < (1000 / frmOptions.txtDelayT) n = n + 1 '************* Check START/PAUSE/STOP Status************* If optPlay.value = False Then If optPause.value = True Then MousePointer = 0 While optPause.value = True DoEvents Wend MousePointer = 11 End If If optPlay.value = False Then MousePointer = 0 Exit Sub End If End If '********************************************************* Wait frmOptions.txtDelayT T1 = Val(Mid(ReadTC("T" & cr), 2, 5)) T2 = Val(Mid(ReadTC("t" & cr), 2, 5)) H = Val(Mid(ReadTC("H" & cr), 2, 5)) fMainForm.UpdateTemp T1, T2, H 'FillData T1, T2, False DoEvents

If Abs(T1 - t) <= Val(frmOptions.txtTempTol) Then GCount = GCount + 1 End If Wend 'FillData T1, T2, True End Sub

Sub GetIV(Channel As Integer, Temp As Single) With frmSetup fNo2 = FreeFile() Open DFileName(Channel) & "_" & Str(Temp) & ".txt" For Output As #fNo2 CNo% = Asc(.TabStrip1.Tabs(Channel).Caption) - 64 CloseSW CNo%, frmSetup.optMidGND lblStatus.Caption = "Taking IV data for ..." & Right(DFileName(Channel), 10) & "_" & Str(Temp) & ".txt"

T2 = Val(Mid(ReadTC("t" & cr), 2, 5)) Print #fNo1, Int(Timer() - tStart); " , "; T2; " Starting point for Channel:"; Channel

Print #fNo2, "Viraj2005 Automated IVT Setup Data File" Print #fNo2, "Sample Name:, "; DFileName(Channel) Print #fNo2, "Description:" Print #fNo2, "No of Graphs & Channel:" Print #fNo2, "Date & Time:, "; Date; ", "; Time Print #fNo2, "Mesa; Area(mm²):"; mesaSize(Channel) Print #fNo2, "Start; V(V):, "; .txtStartV Print #fNo2, "End V (V) :, "; .txtEndV Print #fNo2, "Step V(V):, "; .txtStepV Print #fNo2, "Current limit(mA):, "; .txtCurrentLimit Print #fNo2, "Delay:, "; .txtDelay

180 Print #fNo2, "Avg.:, "; .txtAvg Print #fNo2, "No of Cycles:, "; .txtNoCycle Print #fNo2, "No of Data:, "; ((.txtEndV - .txtStartV) / .txtStepV) + 1 Print #fNo2, "Start Temp(K):, "; .txtStartT Print #fNo2, "End Temp (K):, "; .txtEndT Print #fNo2, "Step Temp(K):, "; .txtStepT Print #fNo2, "Sample Temp(K):, "; Temp Print #fNo2, "Voltage (V)" & " , " & "Current (A)"

Dim V As Single test: SendSM "*RST", stat% If stat% <> 0 Then cho = MsgBox("KEITHLEY 2400 SourceMeter not found", vbRetryCancel + vbExclamation, "GPIB Address Error") If cho = 4 Then GoTo test Else Exit Sub End If End If

SendSM ":OUTPUT ON", stat% StartV = Val(.txtStartV) EndV = Val(.txtEndV) StepV = Val(.txtStepV) NoCycle% = CInt(Val(.txtNoCycle)) ILimit = Val(.txtCurrentLimit) / 1000

For NoSweep% = 1 To NoCycle%

For V = StartV To EndV Step StepV t = Timer() ok = 0 SendSM ":SOUR:VOLT:LEV " & Str(V), stat%

'********************* If Gradient Check ON ************************* If chkGradiCheck.value = 1 Then

While ok = 0 II = 0 SendSM "read?", stat% ReadSM r$ IOld = Val(Mid(r$, 15, 13)) n = 0

For j = 1 To .txtAvg.Text '************* Check START/PAUSE/STOP Status************* If optPlay.value = False Then If optPause.value = True Then MousePointer = 0 While optPause.value = True DoEvents Wend MousePointer = 11 End If If optPlay.value = False Then

181 MousePointer = 0 Close #fNo2 Exit Sub End If End If

'*********************************************************

SendSM "read?", stat% ReadSM r$ INew = Val(Mid(r$, 15, 13))

If IOld < INew Then n = n + 1 If IOld > INew Then n = n - 1 II = II + INew IOld = INew DoEvents Next j

If Abs(n) < 4 Then ok = 1 Wend Else

'********************* If Gradient Check OFF ************************** II = 0 For j = 1 To Val(txtAvg.Text) '************* Check START/PAUSE/STOP Status************* If optPlay.value = False Then If optPause.value = True Then MousePointer = 0 While optPause.value = True DoEvents Wend MousePointer = 11 End If If optPlay.value = False Then MousePointer = 0 Close #fNo2 Exit Sub End If End If

'********************************************************* SendSM "read?", stat% ReadSM r$ INew = Val(Mid(r$, 15, 13)) II = II + INew DoEvents Next j

'**************************************************************** End If VV = Val(Mid(r$, 1, 13)) II = II / txtAvg.Text Print #fNo2, V; " , "; II INew = II

182 '*************** If Current > comp. limit find edge **************** If Abs(INew) > (0.98 * ILimit) Then If Abs(V + StepV) < Abs(V) Then 'Starting edge correction V0 = V V1 = 0 While Abs(INew) > (0.98 * ILimit) Or Abs(INew) < (0.97 * ILimit) V2 = (V0 - V1) / 2 SendSM ":SOUR:VOLT:LEV " & Str(V2), stat% SendSM "read?", stat% ReadSM r$ INew = Val(Mid(r$, 15, 13)) If Abs(INew) > (0.98 * ILimit) Then V0 = V2 Else V1 = V2 End If Wend For FV = V + StepV To V2 Step StepV Print #fNo2, FV; " , "; II Next FV V = FV + StepV

Else 'Ending edge correction For FV = V + StepV To EndV Step StepV Print #fNo2, FV; " , "; II Next FV Exit For End If End If

'******************************************************************* II = 0 pbrCIV.value = Int(Abs(V - StartV) * 100 / Abs(EndV - StartV))

If (V - StartV) Mod 10 * StepV = 0 Then T2 = Val(Mid(ReadTC("t" & cr), 2, 5)) Print #fNo1, Int(Timer() - tStart); " , "; T2 End If Next V

TempStartV = StartV StartV = EndV EndV = TempStartV StepV = -StepV Next NoSweep% End With T2 = Val(Mid(ReadTC("t" & cr), 2, 5)) Print #fNo1, Int(Timer() - tStart); " , "; T2; " End point for Channel:"; Channel

Close #fNo2 End Sub

Sub SetSourceMeter() With frmSetup

183 Iprot$ = ":SENS:CURR:PROT " & Str(.txtCurrentLimit.Text / 1000) VLevel$ = ":SOUR:VOLT:LEV " & .txtStartV.Text SDelay$ = ":SOUR:DEL " & .txtDelay.Text SendSM ":SOUR:FUNC VOLT", stat% SendSM ":SOUR:VOLT:MODE FIXED", stat% SendSM ":SENS:FUNC 'CURR'", stat% SendSM Iprot$, stat% SendSM VLevel$, stat% SendSM ":SENS:CURR:RANG:AUTO ON", stat% SendSM SDelay$, stat% End With End Sub

184 B.2 UV-VIS-NIR detector spectral response characterization

software

The UV, VIS and NIR detector characterization system is controlled using an in-house software package developed with Microsoft Visual Basic. The heart of this setup is the Spectral Products

DK480 monochromator with 3 gratings, a motorized filter wheel, motorized entrance and exit slits.

A schematic diagram of the complete setup is shown in Figure B.12. The motorized mirror is used to select the light source: Deuterium UV lamp, tungsten halogen VIS-NIR or HeNe laser. A multi- sample detector stage has two calibrated detectors: UV enhanced Si and InGaAs photodetectors.

Another four detector positions are available for custom detector characterization. Software features include automatic output light intensity calibration, real time detector spectral response calculation, auto-align detectors for maximum energy, fully automatic light source, grating and filter selection. The DK480 monochromator and SR850 lock-in amplifier are controled through

RS232 and GPIB interfaces, respectively. Mirror and stage stepper motor controllers, shutter, and power unit functions are controlled through the PCI8255 general-purpose PCI board.

185 B.2.1 UV-VIS-NIR setup instrument configuration GPIB SR570 Pre-Amp Current SR560 Pre-Amp SR560 Bias Box AUX 1 AUX Motor Stepper Stepper Controller Si InGaAs PCI8255 Custom 1 Custom 2 Custom RS232 Filter Wheel Filter

SP Motor Power Supply DK 480 Chopper Controller Chopper Monochromator Shutter Shutter Shutter Controller Chopper UV

Source

VIS-NIR VIS-NIR

Source r r

e e

s s

a a

L L

e e

N N

Motor e H Stepper H Controller

Figure B.12 Block diagram of the UV-VIS-NIR detector characterization system.

186

Figure B.13 Photograph of the UV-VIS-NIR detector characterization system.

187

B.2.2 User interfaces

188

189

190

191

192

Figure B.19 The chopper control panel allows the user to set the chopper frequency to one of the preset values or any other custom value. The user can observe the current frequency on the screen.

193

194 B.2.3 Flow chart for the spectral responsivity (UV-VIS-IR) measurement

(Spectral Products monochromator)

Start (sample spectral response measurement) Input parameters from user Set the starting wavelength (λ)

Read the “Advanced Setup” data No λ within the & select the correct grating correct grating spectral range?

Yes

No Read the “Advanced Setup” data λ within the & select the correct filter correct filter spectral range?

Yes

λ within the correct Read the “Advanced Setup” data No light source spectral & select the correct light source range?

Yes

Current sample stage Ask user to verify the sample stage No position is one of the position custom positions ?

Yes

No Need a dark No Open the shutter Shutter spectrum? On? Yes Yes

A B

195

A B

Wait for specified delay time

Read the Lock-in-amplifier

Run “Auto Gain” Yes Lock-in-Amp Run “Auto Reserve” overload?

No Read user specified # of readings with the delay & find the average Plot raw data Light Calculate Responsivity (V/W) Intensity Data Plot light intensity

Plot responsivity Save Data

λ < End Yes Move to next wavelength wavelength? (λ = λ + step)

End

196 B.2.4 Source code

Public fMainForm As frmMain Public MGPIB As Integer Global Intensity(200 To 2960) As Double

Dim FMPos As Integer 'Current position of the filter wheel motor Dim GMPos As Integer 'Current position of the grating motor Dim D(1 To 8) As Integer 'To store 4 8 6 9 forwerd' Dim CNF As Integer 'current data number send to filter wheel motor Dim CNG As Integer 'current data number send to grating motor Dim LPVal As Integer 'Last Port Value The last number sent to printer port

Sub Main() frmSplash.Show frmSplash.Refresh Set fMainForm = New frmMain Load fMainForm Unload frmSplash fMainForm.Show 'd = GetSetting(App.Title, "Settings", "SpeedConst", 100000) Initialize.Visible = True DoEvents Unload Initialize

fn% = FreeFile() Open App.Path & "\Intensity.dat" For Input As #fn% Input #fn%, a, b k = 200 While Not EOF(fn%) And k <= 2960 Input #fn%, a, Intensity(k) If a <> k Then MsgBox "Intensity data file has an error" End If k = k + 1 Wend Close #fn%

End Sub Sub Wait(Time_in_ms As Integer) st = Timer While Timer - st < Time_in_ms / 1000 DoEvents Wend End Sub

Function ChangeUnit(number As Single) As String If Abs(number) < 1 Then number = number * 1000

197 unit = " mV" End If If Abs(number) < 1 Then number = number * 1000 unit = " uV" End If If Abs(number) < 1 Then number = number * 1000 unit = " nV" End If If Abs(number) < 1 Then number = number * 1000 unit = " pV" End If ChangeUnit = Format(number, "000.0000") & unit End Function

Sub MsgWait(Message As String) If Message = "" Then frmMsgBox.Visible = False Else With frmMsgBox .lblMessage.Caption = Message .Visible = True End With End If End Sub

*********************************************************************** DK480_GPIB.bas *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Attribute VB_Name = "DK480_GPIB" Global gblLightSelted As Integer ' Selected light source 1= UV 2= VIS-NIR Global gblDetectorSelted As Integer ' Selected Detector 1=UV enhansed Si 2=InGaAs 3=custom 1 etc.

Sub GoToLamdaCG(WLength&) 'This will rotate the current grating to a new wavelength. "CG" means current Grating. Dim Status% Status% = DKGoto%(WLength& * 100, fMainForm.comComm1, 100) If Status% < 128 Then gblCurWL& = WLength& * 100 Else MsgBox "An error has occurred !", MB_ICONSTOP End If End Sub

Sub GoToLamdaBG(WLength&) 'This will select the best grating and the filter to goto new wavelength. "BG" means Best Grating. Dim CWL& CWL& = gblCurWL& / 100

198

'*********************** To select correct grating ******************** Select Case WLength&

Case Val(frmAdvSetup.txtWL(0)) To Val(frmAdvSetup.txtWL(1)) If gblNGrtSelted& <> 1 Then GrtSel 1 End If

Case Val(frmAdvSetup.txtWL(1)) To Val(frmAdvSetup.txtWL(2)) If gblNGrtSelted& <> 2 Then GrtSel 2 End If

Case Val(frmAdvSetup.txtWL(2)) To Val(frmAdvSetup.txtWL(3)) If gblNGrtSelted& <> 3 Then GrtSel 3 End If Case Else MsgBox "Wavelength " & WLength& & " nm is out of range. Please Check the Advanced Settings."

End Select

'*********************** To select correct Filter ********************

Select Case WLength&

Case Val(frmAdvSetup.txtF(1)) To Val(frmAdvSetup.txtF(2)) If gblFilter% <> 1 Then FltSel 1 End If

Case Val(frmAdvSetup.txtF(2)) To Val(frmAdvSetup.txtF(3)) If gblFilter% <> 2 Then FltSel 2 End If

Case Val(frmAdvSetup.txtF(3)) To Val(frmAdvSetup.txtF(4)) If gblFilter% <> 3 Then FltSel 3 End If

Case Val(frmAdvSetup.txtF(4)) To Val(frmAdvSetup.txtF(5)) If gblFilter% <> 4 Then FltSel 4 End If

Case Val(frmAdvSetup.txtF(5)) To Val(frmAdvSetup.txtF(6)) If gblFilter% <> 5 Then FltSel 5 End If

Case Val(frmAdvSetup.txtF(6)) To 2 * Val(frmAdvSetup.txtF(6)) If gblFilter% <> 6 Then FltSel 6 End If

199

Case Is > 2 * Val(frmAdvSetup.txtF(6)) If gblFilter% <> 6 Then FltSel 6 End If MsgWait "!!!WARNING!!! You Don't have correct filter to block the second orders after the " & Str(2 * Val(frmAdvSetup.txtF(6))) & " nm." DoEvents

Case Else MsgBox "Wavelength " & WLength& & " nm is out of range. Please Check the Advanced Settings."

End Select

'*********************** To Select correct Light Source *************** Select Case WLength&

Case Val(frmAdvSetup.txtLWL(0)) To Val(frmAdvSetup.txtLWL(1)) If gblLightSelted <> 1 Then LightSel 1 End If

Case Val(frmAdvSetup.txtLWL(1)) To Val(frmAdvSetup.txtLWL(2)) If gblLightSelted <> 2 Then LightSel 2 End If

Case Val(frmAdvSetup.txtLWL(2)) To Val(frmAdvSetup.txtLWL(3)) If gblLightSelted <> 3 Then LightSel 3 End If

Case Else MsgBox "Wavelength " & WLength& & " nm is out of the range. System may not have correct lamp. Please Check the Advanced Settings."

End Select

'*********************** To select correct detector ******************* If fMainForm.optMode(2).Value = True And fMainForm.optScan(1).Value = True Then If gblDetectorSelted <> 3 Then DetSel 3 End If Else Select Case WLength& Case Val(frmAdvSetup.txtDWL(0)) To Val(frmAdvSetup.txtDWL(1)) If gblDetectorSelted <> 1 Then DetSel 1 End If

Case Val(frmAdvSetup.txtDWL(1)) To Val(frmAdvSetup.txtDWL(2)) If gblDetectorSelted <> 2 Then DetSel 2 End If

200

Case Else MsgBox "Wavelength " & WLength& & " nm is out of the range. System may not have correct lamp. Please Check the Advanced Settings."

End Select End If

'*********************** Go to wavelength ************************

Status% = DKGoto%(WLength& * 100, fMainForm.comComm1, 100) If Status% < 128 Then gblCurWL& = WLength& * 100 Else MsgBox "An error has occurred !", MB_ICONSTOP End If

End Sub

Sub GrtSel(GrtNo As Integer) MsgWait "Please wait... Selecting Grating # " & GrtNo DoEvents Status% = DKGrtsel%(GrtNo, fMainForm.comComm1, 500) If Status% < 128 Then gblNGrtSelted& = GrtNo Else MsgBox "An error has occurred !", MB_ICONSTOP End If MsgWait "" fMainForm.UpdateMainScreen End Sub

Sub FltSel(FltNo As Integer) Dim Status% On Error GoTo cmdCanOKErr MsgWait "Please wait... Changing to Filter # " & FltNo DoEvents Status% = DKFilter%(FltNo, fMainForm.comComm1, 5) '5: 5s Timeout% If Status% < 128 Then gblFilter% = FltNo gblOkCancel% = IDOK fMainForm.UpdateMainScreen Wait 3000 MsgWait "" DoEvents Exit Sub cmdCanOKErr: MsgBox "Error code is : " & Err, MB_ICONEXCLAMATION

End Sub

Sub SetSlt(SlitNo As Integer, SlitWidth As Integer) Dim Status%, SlitByte% On Error GoTo cmdCanOKErr

If SlitNo = 1 Then SlitByte% = 31 Else SlitByte% = 32

MsgWait "Please wait... Changing to the slit Size"

201 DoEvents Status% = DKSltAdjCal%(SlitByte%, SlitWidth, fMainForm.comComm1, 500) If Status% > 127 Then GoTo cmdCanOKErr

Select Case SlitNo Case 1 gblS1% = SlitWidth ' S1 adjustment. Case 2 gblS2% = SlitWidth ' S2 adjustment. End Select gblOkCancel% = IDOK fMainForm.UpdateMainScreen MsgWait "" Exit Sub cmdCanOKErr: MsgBox "Error code is : " & Err, MB_ICONEXCLAMATION

End Sub

Sub LightSel(LightNo As Integer) ' 1=UV 2=VIS-NIR MsgWait "Please wait... Changing the light Source" DoEvents RunMM frmStpMotSet.txtLmpStp(LightNo - 1) gblLightSelted = LightNo ' MsgBox "Please veryfy the lamp " & Trim(Str(LightNo)) & " power ON"

Wait 3000 MsgWait "" End Sub

Sub DetSel(DetectorNo As Integer) MsgWait "Please wait... Changing the Detector" DoEvents RunDM frmStpMotSet.txtDetStp(DetectorNo - 1) MsgWait "" gblDetectorSelted = DetectorNo MsgBox "Please connect the Detector " & Trim(Str(DetectorNo)) & " to the pre-amp" Wait 2000 End Sub

*********************************************************************** PCI8255V3.bas *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Global ShutOpen As Boolean Global MotPowON As Boolean

202

Dim hWD As Long 'HANDLE Dim pciSlot As WD_PCI_SLOT Dim dwAction As Long Global hET_PCI8255_V3 As ET_PCI8255_V3_HANDLE Dim Opened As Boolean Dim MMPos As Integer 'Mirror Motor Current position Dim DMPos As Integer 'Detector Motor Current position

Const PIB = &H0 'Reset & PIB Cycle Const AUXC = &H2 'Auxuary Direction Const AUXD = &H3 'Auxuary Data Const PA1 = &HC0 'Port-PA 8255#1

Const PB1 = &HC4 'Port-PB 8255#1 Const PC1 = &HC8 'Port-PC 8255#1 Const PCC1 = &HCC& 'Port-Control 8255#1

Const PA2 = &HD0 'Port-PA 8255#2 Const PB2 = &HD4 'Port-PB 8255#2 Const PC2 = &HD8 'Port-PC 8255#2 Const PCC2 = &HDC 'Port Control 8255#2

Const PA3 = &HE0 'Port-PA 8255#3 Const PB3 = &HE4 'Port-PB 8255#3 Const PC3 = &HE8 'Port-PC 8255#3 Const PCC3 = &HEC 'Port Control 8255#3

Const BIT0_ON = &H1 '0000 0001 OR XXXX XXXX = XXXX XXX1 Const BIT0_OFF = &HFE '1111 1110 AND XXXX XXXX = XXXX XXX0

Const BIT1_ON = &H2 '0000 0010 OR XXXX XXXX = XXXX XX1X Const BIT1_OFF = &HFD '1111 1101 AND XXXX XXXX = XXXX XX0X

Const BIT2_ON = &H4 '0000 0100 OR XXXX XXXX = XXXX X1XX Const BIT2_OFF = &HFB '1111 1011 AND XXXX XXXX = XXXX X0XX

Const BIT3_ON = &H8 '0000 1000 OR XXXX XXXX = XXXX 1XXX Const BIT3_OFF = &HF7 '1111 0111 AND XXXX XXXX = XXXX 0XXX

Const BIT4_ON = &H10 '0001 0000 OR XXXX XXXX = XXX1 XXXX Const BIT4_OFF = &HEF '1110 1111 AND XXXX XXXX = XXX0 XXXX

Const BIT5_ON = &H20 '0010 0000 OR XXXX XXXX = XX1X XXXX Const BIT5_OFF = &HDF '1101 1111 AND XXXX XXXX = XX0X XXXX

Const BIT6_ON = &H40 '0100 0000 OR XXXX XXXX = X1XX XXXX Const BIT6_OFF = &HBF '1011 1111 AND XXXX XXXX = X0XX XXXX

Const BIT7_ON = &H80 '1000 0000 OR XXXX XXXX = 1XXX XXXX

203 Const BIT7_OFF = &H7F '0111 1111 AND XXXX XXXX = 0XXX XXXX

Dim DFSW(1 To 4) As Byte 'Data for Full Step Wave step sequence Dim DHS(1 To 8) As Byte 'Data for Half Step sequence Dim DFSHT(1 To 4) As Byte 'Data for Full Step High Torque sequence

Sub initializePCI8255() Dim InOutData As Byte Dim ControlWord As Byte

'Step data for Full Step Wave. This is "or" data, "and" data = &H5 + &HC0 DFSW(1) = &H5 DFSW(2) = &H12 DFSW(3) = &H9 DFSW(4) = &H22

'Step data for Full Steps High Torque. This is "or" data, "and" data = &H5 + &HC0 DFSHT(1) = &H27 DFSHT(2) = &H17 DFSHT(3) = &H1B DFSHT(4) = &H2B

'Step data for Half Steps. This is "or" data, "and" data = &H5 + &HC0 DHS(1) = &H5 DHS(2) = &H27 DHS(3) = &H22 DHS(4) = &H2B DHS(5) = &H9 DHS(6) = &H1B DHS(7) = &H12 DHS(8) = &H3F

Opened = False If Not PCI_Get_WD_handle(hWD) Then Exit Sub 'Make sure Driver is loaded WD_Close (hWD) If Not Opened Then Opened = ET_PCI8255_V3_LocateAndOpenBoard(ET_PCI8255_V3_DEFAULT_VENDOR_ID, ET_PCI8255_V3_DEFAULT_DEVICE_ID, hET_PCI8255_V3) End If If Opened Then InOutData = ET_PCI8255_V3_ReadByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), PIB) 'Read PIB Reset Port InputData = InOutData And BIT0_OFF 'Bit0 = EXTRST# = "0" (Reset:RES#) InOutData = InOutData Or BIT5_ON 'Bit5:4 = 11 = PIB Cycle Slowest InOutData = InOutData Or BIT4_ON Call ET_PCI8255_V3_WriteByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), PIB, InOutData) 'Active RES#

204 InOutData = ET_PCI8255_V3_ReadByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), AUXD) 'Read Aux Data Port InputData = InOutData And BIT0_OFF 'Bit0 = Aux0 = "0" (Enable CS) InOutData = InOutData Or BIT4_ON 'Bit4 = Aux4 = "1" (Relay OFF) Call ET_PCI8255_V3_WriteByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), AUXD, InOutData) 'Active Chips Select & Relay

InOutData = ET_PCI8255_V3_ReadByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), AUXC) 'Read Aux Direction Port InOutData = InOutData Or BIT4_ON 'Aux4 = Output InOutData = InOutData Or BIT0_ON 'Aux0 = Output Call ET_PCI8255_V3_WriteByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), AUXC, InOutData) 'Setup Aux Direction

End If ControlWord = &H88 Call ET_PCI8255_V3_WriteByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), PCC1, ControlWord) 'Control 8255#1 = PC (high bits) is Input

End Sub

Sub InitializeMM() 'initialize Mirror motor For k = 1 To 5 'HalfStep PA1, "F" FullStepHT PA1, "R" Wait 50 DoEvents Next k If ReadPC1(5) = False Then For k = 1 To 30 'HalfStep PA1, "F" FullStepHT PA1, "R" Wait 50 DoEvents Next k End If k = 1 While ReadPC1(5) = True And k < 160 'HalfStep PA1, "R" FullStepHT PA1, "F" k = k + 1 Wait 50 DoEvents Wend MMPos = 0 RunMM frmStpMotSet.txtLmpStp(1) gblLightSelted = 2 End Sub Sub InitializeDM() 'initialize Detector motor If ReadPC1(4) = True Then For k = 1 To 40

205 FullStepHT PB1, "F" Wait 1 DoEvents Next k End If k = 1 While ReadPC1(4) = False And k < 1840 FullStepHT PB1, "R" k = k + 1 Wait 1 DoEvents Wend DMPos = 0 RunDM frmStpMotSet.txtDetStp(0) gblDetectorSelted = 1 End Sub

Sub RunMM(NewPos As Integer) 'To rotate Mirror motor to new position While MMPos < NewPos 'HalfStep PA1, "F" 'FullStepHT PA1, "F" FullStepW PA1, "F" MMPos = MMPos + 1 DoEvents Wait 50 Wend While MMPos > NewPos 'HalfStep PA1, "R" 'FullStepHT PA1, "R" FullStepW PA1, "R" MMPos = MMPos - 1 DoEvents Wait 50 Wend

End Sub

Sub RunDM(NewPos As Integer) 'To rotate Detector motor to new position While DMPos < NewPos 'HalfStep Pb1, "F" FullStepHT PB1, "F" 'FullStepW PB1, "F" DMPos = DMPos + 1 DoEvents Wait 1 Wend While DMPos > NewPos 'HalfStep Pb1, "R" FullStepHT PB1, "R" 'FullStepW PB1, "R" DMPos = DMPos - 1 DoEvents Wait 1 Wend

206 End Sub

Sub FullStepW(MotorPort As Long, Direction_F_R As String) 'Run the motor 1 step using Full Step Wave sequence Dim InOutData As Byte Dim CheckData As Byte Dim SNo As Integer SNo = 0

InOutData = ET_PCI8255_V3_ReadByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), MotorPort) ' Read Output Latch Port

For k = 1 To 4 If (InOutData Or DFSW(k)) = InOutData Then SNo = k ' find out current step no Next k If SNo = 0 Then SNo = 1

If UCase(Direction_F_R) = "F" Then If SNo < 4 Then SNo = SNo + 1 Else SNo = 1 End If Else If SNo > 1 Then SNo = SNo - 1 Else SNo = 4 End If End If InOutData = InOutData Or DFSW(SNo) 'make "1"s in the new bit pattern witout changeing unused bits InOutData = InOutData And (DFSW(SNo) + &HC0) 'make "0"s in the new bit pattern witout changeing unused bits

Call ET_PCI8255_V3_WriteByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), MotorPort, InOutData) ' Update Port

End Sub

Sub FullStepHT(MotorPort As Long, Direction_F_R As String) 'Run the motor 1 step using Full Step High Torque sequence Dim InOutData As Byte Dim CheckData As Byte Dim SNo As Integer SNo = 0

InOutData = ET_PCI8255_V3_ReadByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), MotorPort) ' Read Output Latch Port

For k = 1 To 4 If (InOutData Or DFSHT(k)) = InOutData Then SNo = k ' find out current step no Next k If SNo = 0 Then SNo = 1

207

If UCase(Direction_F_R) = "F" Then If SNo < 4 Then SNo = SNo + 1 Else SNo = 1 End If Else If SNo > 1 Then SNo = SNo - 1 Else SNo = 4 End If End If InOutData = InOutData Or DFSHT(SNo) 'make "1"s in the new bit pattern witout changeing unused bits InOutData = InOutData And (DFSHT(SNo) + &HC0) 'make "0"s in the new bit pattern witout changeing unused bits

Call ET_PCI8255_V3_WriteByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), MotorPort, InOutData) ' Update Port

End Sub

Sub HalfStep(MotorPort As Long, Direction_F_R As String) 'Run the motor 1 step using Half Step Wave sequence Dim InOutData As Byte Dim CheckData As Byte Dim SNo As Integer SNo = 0

InOutData = ET_PCI8255_V3_ReadByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), MotorPort) ' Read Output Latch Port

For k = 1 To 8 If (InOutData Or DHS(k)) = InOutData Then SNo = k ' To find out current step no Next k If SNo = 0 Then SNo = 1

If UCase(Direction_F_R) = "F" Then If SNo < 8 Then SNo = SNo + 1 Else SNo = 1 End If Else If SNo > 1 Then SNo = SNo - 1 Else SNo = 8 End If End If InOutData = InOutData Or DHS(SNo) 'make "1"s in the new bit pattern witout changeing unused bits InOutData = InOutData And (DHS(SNo) + &HC0) 'make "0"s in the new bit pattern witout changeing unused bits

208 Call ET_PCI8255_V3_WriteByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), MotorPort, InOutData) ' Update Port

End Sub

Function ReadPC1(BitNo) As Boolean Dim InOutData As Byte Dim CheckData As Byte Dim BITx_ON As Byte BITx_ON = 2 ^ BitNo InOutData = ET_PCI8255_V3_ReadByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), PC1) 'Read Input/Output Latch of Port-C1 CheckData = InOutData And BITx_ON If CheckData = BITx_ON Then ReadPC1 = True Else ReadPC1 = False

End Function Sub Shutter(open_close As String) Dim InOutData As Byte

InOutData = ET_PCI8255_V3_ReadByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), PA1) ' Read Output Latch Port-A

If UCase(open_close) = "CLOSE" Then InOutData = InOutData And BIT6_OFF ' PA6 = "0" (1011 1111) ShutOpen = False Else InOutData = InOutData Or BIT6_ON ' PA6 = "1" (0100 0000) ShutOpen = True End If

Call ET_PCI8255_V3_WriteByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), PA1, InOutData) ' Update Port-A

End Sub

Sub MotorPower(On_Off As String) Dim InOutData As Byte

InOutData = ET_PCI8255_V3_ReadByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), PA1) ' Read Output Latch Port-A

If UCase(On_Off) = "ON" Then InOutData = InOutData And BIT7_OFF ' PA6 = "0" (1011 1111) MotPowON = True Else InOutData = InOutData Or BIT7_ON ' PA6 = "1" (0100 0000) MotPowON = False End If

Call ET_PCI8255_V3_WriteByte(hET_PCI8255_V3, CByte(ET_PCI8255_V3_AD_BAR0), PA1, InOutData) ' Update Port-A

End Sub

209

Sub ClosePort() If Opened Then Call ET_PCI8255_V3_Close(hET_PCI8255_V3) Opened = False End Sub

*********************************************************************** SR850_GPIB.bas *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Attribute VB_Name = "SR850_GPIB" Global CStep As Integer 'Current step No of Stepper motor Global IniOK As Boolean ' To check correctly Initialized the stepper motor Global PauseStop As Integer 'To check user press [Pause] or [Stop] play=0 pause=1 Stop =2 Global AutoTrack As Boolean Const BDINDEX = 0 ' Board Index Const PRIMARY_ADDR_OF_DMM = 8 ' Primary address of device Const NO_SECONDARY_ADDR = 0 ' Secondary address of device Const Timeout = T10s ' Timeout value = 10 seconds Const EOTMODE = 1 ' Enable the END message Const EOSMODE = 0 ' Disable the EOS mode

Const ARRAYSIZE = 1024 ' Size of read buffer

Dim ErrMsg As String * 100 Dim Dev As Integer Dim ErrorMnemonic Dim ValueStr As String * ARRAYSIZE Dim Response As Integer

'To read Data (R)from SR850 (while scaning) Function SR850Data() ilwrt Dev%, "OUTP? 3", 7 If (ibsta And EERR) Then Call GPIBCleanup("Unable to write to device") End If

ilrd Dev%, ValueStr, Len(ValueStr) If (ibsta And EERR) Then Call GPIBCleanup("Unable to read from device") End If SR850Data = Val(Left$(ValueStr, ibcntl - 1))

End Function 'To read averaged Data from SR850 Function SR850AvgData(NoOfAvg As Integer, Delay As Integer) DataSum = 0 For k = 1 To NoOfAvg DataSum = DataSum + SR850Data Wait Delay Next k

210 SR850AvgData = DataSum / NoOfAvg End Function

'To write command to SR850 Sub WriteToSR850(CommandString As String) ilwrt Dev%, CommandString, Len(CommandString) If (ibsta And EERR) Then Call GPIBCleanup("Unable to write to device") End If End Sub

'To read Data from SR850 Function ReadSR850() ilrd Dev%, ValueStr, Len(ValueStr) If (ibsta And EERR) Then Call GPIBCleanup("Unable to read from device") End If ReadSR850 = Val(Left$(ValueStr, ibcntl - 1)) End Function

Sub InitializeGPIB() Dev% = ildev(BDINDEX, PRIMARY_ADDR_OF_DMM, NO_SECONDARY_ADDR, _ Timeout, EOTMODE, EOSMODE) If (ibsta And EERR) Then ErrMsg = "Unable to open device" & Chr(13) & "ibsta = &H" & _ Chr(13) & Hex(ibsta) & "iberr = " & iberr MsgBox ErrMsg, vbCritical, "Error" End End If ' The application resets the GPIB portion of the device by calling ' ilclr. ilclr Dev% If (ibsta And EERR) Then Call GPIBCleanup("Unable to clear device") End If ilwrt Dev%, "OUTX 1", 6 If (ibsta And EERR) Then Call GPIBCleanup("Unable to write to device") End If

End Sub

Sub GPIBCleanup(Msg$)

ErrorMnemonic = Array("EDVR", "ECIC", "ENOL", "EADR", "EARG", _ "ESAC", "EABO", "ENEB", "EDMA", "", _ "EOIP", "ECAP", "EFSO", "", "EBUS", _ "ESTB", "ESRQ", "", "", "", "ETAB")

ErrMsg$ = Msg$ & Chr(13) & "ibsta = &H" & Hex(ibsta) & Chr(13) _ & "iberr = " & iberr & " <" & ErrorMnemonic(iberr) & ">"

211 MsgBox ErrMsg$, vbCritical, "Error" ilonl Dev%, 0

End Sub

Sub InitializeSR850() WriteToSR850 "FMOD2" 'reference source "external" WriteToSR850 "RSLP1" 'reference slope sine zero crossing (i=0), TTL rising edge (i=1), TTL falling edge (i=2) WriteToSR850 "HARM1" 'detection harmonic 1 WriteToSR850 "ISRC0" WriteToSR850 "IGND0" WriteToSR850 "ICPL0" 'input coupling AC WriteToSR850 "ILIN0" 'input line notch filter status no filters (i=0), Line notch in (i=1), 2xLine notch in (i=2) or Both notch filters in (i=3).. WriteToSR850 "OFSL1" WriteToSR850 "SYNC1" WriteToSR850 "SMOD1" 'The SMOD command sets or queries the screen format. The parameter i selects Single or full screen display (i=0), or Up/Down dual display (i=1). WriteToSR850 "MNTR1" 'monitor display mode. WriteToSR850 "DTYP1,2" 'display type. WriteToSR850 "DTYP2,2" WriteToSR850 "DTRC1,3 " 'displayed trace number. WriteToSR850 "DTRC2,4 " 'displayed trace number. 'WriteToSR850 "" 'WriteToSR850 ""

End Sub

Function TimeConstant() As String WriteToSR850 "OFLT?" TCNo = ReadSR850 Select Case TCNo Case 0 TimeConstant = "10 us" Case 1 TimeConstant = "30 us" Case 2 TimeConstant = "100 us" Case 3 TimeConstant = "300 us" Case 4 TimeConstant = "1 ms" Case 5 TimeConstant = "3 ms" Case 6 TimeConstant = "10 ms" Case 7 TimeConstant = "30 ms" Case 8 TimeConstant = "100 ms" Case 9 TimeConstant = "300 ms" Case 10 TimeConstant = "1 s" Case 11

212 TimeConstant = "3 s" Case 12 TimeConstant = "10 s" Case 13 TimeConstant = "30 s" Case 14 TimeConstant = "100 s" Case 15 TimeConstant = "300 s" Case 16 TimeConstant = "1 ks" Case 17 TimeConstant = "3 ks" Case 18 TimeConstant = "10 ks" Case 19 TimeConstant = "30 ks" End Select End Function

Function TimeConsSec() As Single WriteToSR850 "OFLT?" TCNo = ReadSR850 Select Case TCNo Case 0 TimeConsSec = 0.00001 Case 1 TimeConsSec = 0.00003 Case 2 TimeConsSec = 0.0001 Case 3 TimeConsSec = 0.0003 Case 4 TimeConsSec = 0.001 Case 5 TimeConsSec = 0.003 Case 6 TimeConsSec = 0.01 Case 7 TimeConsSec = 0.03 Case 8 TimeConsSec = 0.1 Case 9 TimeConsSec = 0.3 Case 10 TimeConsSec = 1 Case 11 TimeConsSec = 3 Case 12 TimeConsSec = 10 Case 13 TimeConsSec = 30 Case 14 TimeConsSec = 100 Case 15 TimeConsSec = 300 Case 16

213 TimeConsSec = 1000 Case 17 TimeConsSec = 3000 Case 18 TimeConsSec = 10000 Case 19 TimeConsSec = "30 ks" End Select End Function Function Sensitivity() As Double WriteToSR850 "SENS?" SensNo = ReadSR850 Select Case SensNo Case 0 Sensitivity = 0.000000002 Case 1 Sensitivity = 0.000000005 Case 2 Sensitivity = 0.00000001 Case 3 Sensitivity = 0.00000002 Case 4 Sensitivity = 0.00000005 Case 5 Sensitivity = 0.0000001 Case 6 Sensitivity = 0.0000002 Case 7 Sensitivity = 0.0000005 Case 8 Sensitivity = 0.000001 Case 9 Sensitivity = 0.000002 Case 10 Sensitivity = 0.000005 Case 11 Sensitivity = 0.00001 Case 12 Sensitivity = 0.00002 Case 13 Sensitivity = 0.00005 Case 14 Sensitivity = 0.0001 Case 15 Sensitivity = 0.0002 Case 16 Sensitivity = 0.0005 Case 17 Sensitivity = 0.001 Case 18 Sensitivity = 0.002 Case 19 Sensitivity = 0.005 Case 20 Sensitivity = 0.01 Case 21 Sensitivity = 0.02

214 Case 22 Sensitivity = 0.05 Case 23 Sensitivity = 0.1 Case 24 Sensitivity = 0.2 Case 25 Sensitivity = 0.5 Case 26 Sensitivity = 1 End Select End Function

Function ChkOverload(Point As Integer) As Boolean 'Point 0 = INPUT or RESRV overload 'Point 1 = FILTR overload 'Point 2 = OUTPT overload

WriteToSR850 "LIAS?" & Trim(Str(Point)) ChkOverload = ReadSR850

End Function

Sub SetGain() 'if overload detected decrease the sensitivity WriteToSR850 "SENS?" cgain = ReadSR850 If ChkOverload(2) Then MsgWait "Output Overload Detected! Gain is increasing...." Wait 1000

While ChkOverload(2) And cgain < 26 WriteToSR850 "SENS?" cgain = ReadSR850 WriteToSR850 "SENS" & Trim(Str(cgain + 1)) Wait 2000 Wend MsgWait "" If cgain = 26 Then MsgBox "Output is too high ! Please reduse pre amp gain or light intensity" End If

ElseIf AutoTrack = True Then If SR850AvgData(5, CInt(TimeConsSec * 1000)) < 0.1 * Sensitivity Then WriteToSR850 "SENS" & Trim(Str(cgain - 1)) Wait 2000 End If End If

End Sub

*********************************************************************** ModSaveFormData.bas ***********************************************************************

215 ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Attribute VB_Name = "ModSaveFormData" Option Explicit

Public Sub ReadFormData(frm As Form, FileName As String, Optional ByRef LoadError As Boolean)

Dim ctrl As Control, f As Integer, cval As Variant, cname As String, idx As Variant, cidx As Variant Dim j As Integer, lstcnt As Integer, lstidx As Integer f = FreeFile() On Error Resume Next Open FileName For Input As #f If Err.Number = 53 Then Exit Sub 'File not found Err.Clear

Input #f, cname If Not cname Like App.FileDescription Then Close #f MsgBox "File is not a " & App.FileDescription & " Data File", vbExclamation + vbOKOnly, "Error reading file" LoadError = True Exit Sub End If

While Not EOF(f) Input #f, cname, cval, idx For Each ctrl In frm.Controls Err.Clear cidx = Null With ctrl If .Name = cname Then cidx = .Index If TypeName(cidx) = "Null" Or cidx = idx Then If TypeOf ctrl Is CheckBox Then .value = cval

ElseIf TypeOf ctrl Is OptionButton Then .value = cval

ElseIf TypeOf ctrl Is TextBox Then .Text = cval

ElseIf TypeOf ctrl Is ComboBox Then .ListIndex = cval

ElseIf TypeOf ctrl Is ListBox Then lstidx = cval Input #f, lstcnt .Clear For j = 1 To lstcnt Input #f, cval

216 .AddItem cval Next .ListIndex = lstidx End If Exit For End If End If End With Next ctrl Wend

Close #f

End Sub

Public Sub SaveFormData(frm As Form, FileName As String)

Dim ctrl As Control, f As Integer, idx As Variant, j As Integer f = FreeFile()

Open FileName For Output As #f

Write #f, App.FileDescription On Error Resume Next

For Each ctrl In frm.Controls Err.Clear idx = Null With ctrl idx = .Index If TypeOf ctrl Is CheckBox Then Print #f, .Name Write #f, .value Write #f, idx

ElseIf TypeOf ctrl Is OptionButton Then Print #f, .Name Write #f, .value Write #f, idx

ElseIf TypeOf ctrl Is TextBox Then Print #f, .Name Write #f, .Text Write #f, idx

ElseIf TypeOf ctrl Is ComboBox Then Print #f, .Name Write #f, .ListIndex Write #f, idx

ElseIf TypeOf ctrl Is ListBox Then Print #f, .Name Write #f, .ListIndex Write #f, idx Write #f, .ListCount For j = 1 To .ListCount

217 Write #f, .List(j - 1) Next

End If

End With Next ctrl

Close #f

End Sub

*********************************************************************** frmInitialize.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private Sub cmdIgnore_Click() IniOK = False Me.Visible = False End Sub

Private Sub Form_Activate()

Dim I%, Baud$ ' On Error GoTo FormErr

IniOK = False pBarInitialize.Value = 10

gblIniExist% = GetDkInit%() If gblIniExist% Then If COMInit%(gblPortNo%, gblBaud%) Then 'Initializing dk successfully. Do nothing. Else SetCOM.Show MODAL End If Else SetCOM.Show MODAL End If If gblInitCom% Then 'If CM110, gblType% = 0; if CM112, gblType%=1 or 254 If gblType% = 0 Then 'if CM110 'mnuType.Enabled = False 'mnuIncDec2.Enabled = False Else 'mnuType.Enabled = True 'mnuIncDec2.Enabled = True End If gblFilter% = 1 InitQueries fMainForm.UpdateMainScreen End If

218 'AlignGotoBar pBarInitialize.Value = 60 lblMessage = "Initialize Lock-in Amplifier SR850"

InitializeGPIB pBarInitialize.Value = 80

InitializeSR850 pBarInitialize.Value = 100 fMainForm.UpdateMainScreen pBarInitialize.Value = 5 lblMessage = "Initializing PCI8255 interface card" DoEvents initializePCI8255 pBarInitialize.Value = 20 lblMessage = "Power up Motor Powersupply" MotorPower "ON" Wait 1000 Shutter "Open" fMainForm.UpdateMainScreen pBarInitialize.Value = 30 lblMessage = "Checking Shutter..." DoEvents Shutter "Close" Wait 500 Shutter "Open" lblMessage = "Initializing Mirror Stepper Motor" DoEvents InitializeMM pBarInitialize.Value = 50 lblMessage = "Initializing Detector Stepper Motor" DoEvents InitializeDM pBarInitialize.Value = 100

Wait 500

IniOK = True Me.Visible = False

FormResume: Exit Sub

FormErr: MsgBox "Error code is : " & Err, MB_ICONEXCLAMATION Resume FormResume

End Sub

Private Sub AlignGotoBar() Dim LeftVar!, TopVar!, HeightVar!, WidthVar!

219 Dim I%

' 'HeightVar! = picStep(0).Height ' TopVar! = picStep(0).Top

'For I% = 1 To 4 ' WidthVar! = picStep(I%).Width ' LeftVar! = picStep(I% - 1).Left + picStep(I% - 1).Width ' picStep(I%).Move LeftVar!, TopVar!, WidthVar!, HeightVar! ' Next I% End Sub

Private Bpress As Boolean Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Any) As Long Const EM_UNDO = &HC7 Private Declare Function OSWinHelp% Lib "user32" Alias "WinHelpA" (ByVal hwnd&, ByVal HelpFile$, ByVal wCommand%, dwData As Any)

Private Sub cmdCyclePlay_Click() If IniOK = False Then ch = MsgBox("Hardware NOT initialized." & Chr(10) & Chr(13) & "Would you like to start initialize now", vbYesNo, "Initialize Error") If ch = 7 Then Exit Sub End If Initialize.Visible = True Unload Initialized End If PauseStop = 0 If txtStart < 400 Then txtStart = 400 If txtStart > 1250 Then txtStart = 1250 If Abs(gblCurWL& - txtStart.Text) < Abs(gblCurWL& - txtStop.Text) Then ActiveForm.PlayScan txtStart.Text, txtStep.Text, txtStop.Text, txtDelay, txtAvg, False ActiveForm.PlayScan txtStop.Text, -txtStep.Text, txtStart.Text, txtDelay, txtAvg, False Else ActiveForm.PlayScan txtStop.Text, -txtStep.Text, txtStart.Text, txtDelay, txtAvg, False ActiveForm.PlayScan txtStart.Text, txtStep.Text, txtStop.Text, txtDelay, txtAvg, False End If

End Sub

Private Sub cmdFF_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)

220 If Button = 2 Then ' GoToLamdaCG InputBox("Enter Wavelength that You need to go", "Go to Lamda", 1000) Else Bpress = True While Bpress = True ' GoG 1, "F" ' Wait 0.3 ' DoEvents Wend End If End Sub

Private Sub cmdFF_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single) Bpress = False End Sub

Private Sub cmdFFU_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single) WriteToSR850 "OUTP?3" UpdateDispData ReadSR850 Bpress = False End Sub

Private Sub cmdMotPow_Click() If MotPowON Then MotorPower "OFF" shpMPwLED.FillColor = &H0 Else MotorPower "ON" shpMPwLED.FillColor = &HFF& MsgWait "Please wait Initilizing Stepper Motors" InitializeMM InitializeDM MsgWait "" End If End Sub

Private Sub cmdPause_Click() If PauseStop = 1 Then MsgWait "" PauseStop = 0 Else MsgWait "Scan Pause by User. Press Pause agian to continue." DoEvents PauseStop = 1 Me.cmdPlay.Enabled = False

End If End Sub

Private Sub cmdREV_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) If Button = 2 Then ' GotoLamdacg InputBox("Enter Wavelength that You need to go", "Go to Lamda", 1000)

221 Else Bpress = True While Bpress = True ' GotoLamda gblCurWL& - 1 'DoEvents Wend End If End Sub

Private Sub cmdREV_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single) WriteToSR850 "OUTP?3" UpdateDispData ReadSR850 Bpress = False End Sub

Private Sub cmdREVU_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single) WriteToSR850 "OUTP?3" UpdateDispData ReadSR850 Bpress = False End Sub

Private Sub cmdPlay_Click() cmdPlay.Enabled = False cmdPause.Enabled = True cmdStop.Enabled = True PauseStop = 0

If optMode(2).Value = True And optScan(1).Value = True Then If IniOK = False Then ch = MsgBox("Hardware NOT initialized." & Chr(10) & Chr(13) & "Would you like to start initialize now", vbYesNo, "Initialize Error") If ch = 7 Then Exit Sub End If Initialize.Visible = True Unload Initialized End If 'If txtStart < 400 Then txtStart = 400 'If txtStart > 1250 Then txtStart = 1250 'ActiveForm.SetScale txtStart, txtStop ActiveForm.ScanSample txtStart.Text, txtStep.Text, txtStop.Text, txtDelay, txtAvg End If

If optMode(2).Value = True And optScan(0).Value = True Then If IniOK = False Then ch = MsgBox("Hardware NOT initialized." & Chr(10) & Chr(13) & "Would you like to start initialize now", vbYesNo, "Initialize Error") If ch = 7 Then Exit Sub End If Initialize.Visible = True Unload Initialized End If

222 ActiveForm.Calibrate txtStart.Text, txtStep.Text, txtStop.Text, txtDelay, txtAvg End If

'ABS Background mode If optMode(1).Value = True And optScan(0).Value = True Then ActiveForm.ScanABSBakGnd txtStart.Text, txtStep.Text, txtStop.Text, txtDelay, txtAvg End If

End Sub

Private Sub cmdStop_Click() PauseStop = 2 cmdPlay.Enabled = True cmdPause.Enabled = False cmdStop.Enabled = False MsgWait "" End Sub

Private Sub frmShutter_Click() If shpShutter.FillColor = &H8000000F Then Shutter "close" lblShutter.Caption = "Closed" shpShutter.FillColor = &H0 Else Shutter "open" lblShutter.Caption = "Open" shpShutter.FillColor = &H8000000F End If End Sub

Private Sub MDIForm_Load() ReadFormData Me, App.Path & "\Settings_Main.dat"

Me.Left = GetSetting(App.Title, "Settings", "MainLeft", 1000) Me.Top = GetSetting(App.Title, "Settings", "MainTop", 1000) Me.Width = GetSetting(App.Title, "Settings", "MainWidth", 7500) Me.Height = GetSetting(App.Title, "Settings", "MainHeight", 6500) MGPIB = GetSetting(App.Title, "Settings", "GPIB", 8) 'Me.txtGPIB = MGPIB LoadNewDoc End Sub

Private Sub LoadNewDoc() Static lDocumentCount As Long Dim frmD As frmDocument lDocumentCount = lDocumentCount + 1 Set frmD = New frmDocument frmD.Caption = "Spectrum Book " & lDocumentCount frmD.Width = Me.Width - 5960 frmD.Height = Me.Height - 2100 frmD.Show frmD.Refresh End Sub

223

Private Sub MDIForm_Unload(Cancel As Integer) SaveFormData Me, App.Path & "\Settings_Main.dat"

If Me.WindowState <> vbMinimized Then SaveSetting App.Title, "Settings", "MainLeft", Me.Left SaveSetting App.Title, "Settings", "MainTop", Me.Top SaveSetting App.Title, "Settings", "MainWidth", Me.Width SaveSetting App.Title, "Settings", "MainHeight", Me.Height SaveSetting App.Title, "Settings", "GPIB", MGPIB End If MotorPower "OFF" Shutter "Close" ilonl Dev%, 0 ClosePort Close All End End Sub

Private Sub optMode_Click(Index As Integer) If Index = 0 Then frmMonitor.Show vbModal, Me End If If Index = 1 Then optScan(0).Caption = "BakGnd" End If If Index = 2 Then optScan(0).Caption = "Calibrate" End If

End Sub

Private Sub tbAdvStp_Click() frmAdvSetup.Visible = True End Sub

Private Sub tbChopper_Click() frmChopper.Show MODAL End Sub

Private Sub tbFilter_Click() If gblInitCom% Then ctrFilter.Show MODELESS UpdateMainScreen Else MsgBox "Did you initialize a serial port ? " End If End Sub

Private Sub tbSR850_Click() frmSR850.Visible = True End Sub

Private Sub tbToolBar_ButtonClick(ByVal Button As MSComctlLib.Button) On Error Resume Next

224 Select Case Button.Key Case "New" LoadNewDoc Case "Open" mnuFileOpen_Click Case "Save" mnuFileSave_Click Case "Multi" Static v If v = 0 Then v = 1 Else v = 0 frmSR850.Visible = v Button.Value = v Case "IV"

Case "Setting"

Case "Print" mnuFilePrint_Click Case "Cut" mnuEditCut_Click Case "Copy" mnuEditCopy_Click Case "Paste" mnuEditPaste_Click Case "Bold" ' ActiveForm.rtfText.SelBold = Not ActiveForm.rtfText.SelBold ' Button.Value = IIf(ActiveForm.rtfText.SelBold, tbrPressed, tbrUnpressed) Case "Italic" ' ActiveForm.rtfText.SelItalic = Not ActiveForm.rtfText.SelItalic ' Button.Value = IIf(ActiveForm.rtfText.SelItalic, tbrPressed, tbrUnpressed) Case "Underline" ' ActiveForm.rtfText.SelUnderline = Not ActiveForm.rtfText.SelUnderline ' Button.Value = IIf(ActiveForm.rtfText.SelUnderline, tbrPressed, tbrUnpressed) Case "Align Left" ' ActiveForm.rtfText.SelAlignment = rtfLeft Case "Center" ' ActiveForm.rtfText.SelAlignment = rtfCenter Case "Align Right" ' ActiveForm.rtfText.SelAlignment = rtfRight Case "Drawing" 'ToDo: Add 'Drawing' button code. End Select End Sub

Private Sub mnuHelpAbout_Click() frmAbout.Show vbModal, Me End Sub

Private Sub mnuHelpSearchForHelpOn_Click() Dim nRet As Integer

'if there is no helpfile for this project display a message to the user

225 'you can set the HelpFile for your application in the 'Project Properties dialog If Len(App.HelpFile) = 0 Then MsgBox "Unable to display Help Contents. There is no Help associated with this project.", vbInformation, Me.Caption Else On Error Resume Next nRet = OSWinHelp(Me.hwnd, App.HelpFile, 261, 0) If Err Then MsgBox Err.Description End If End If

End Sub

Private Sub mnuHelpContents_Click() SetupFigure.Visible = True Exit Sub Dim nRet As Integer

'if there is no helpfile for this project display a message to the user 'you can set the HelpFile for your application in the 'Project Properties dialog If Len(App.HelpFile) = 0 Then MsgBox "Unable to display Help Contents. There is no Help associated with this project.", vbInformation, Me.Caption Else On Error Resume Next nRet = OSWinHelp(Me.hwnd, App.HelpFile, 3, 0) If Err Then MsgBox Err.Description End If End If

End Sub

Private Sub mnuWindowArrangeIcons_Click() Me.Arrange vbArrangeIcons End Sub

Private Sub mnuWindowTileVertical_Click() Me.Arrange vbTileVertical End Sub

Private Sub mnuWindowTileHorizontal_Click() Me.Arrange vbTileHorizontal End Sub

Private Sub mnuWindowCascade_Click() Me.Arrange vbCascade End Sub

Private Sub mnuWindowNewWindow_Click() LoadNewDoc End Sub

226 Private Sub mnuToolsOptions_Click() frmOptions.Show vbModal, Me End Sub

Private Sub mnuViewOptions_Click() frmOptions.Show vbModal, Me End Sub

Private Sub mnuViewRefresh_Click() 'ToDo: Add 'mnuViewRefresh_Click' code. MsgBox "Add 'mnuViewRefresh_Click' code." End Sub

Private Sub mnuViewStatusBar_Click() mnuViewStatusBar.Checked = Not mnuViewStatusBar.Checked sbStatusBar.Visible = mnuViewStatusBar.Checked End Sub

Private Sub mnuViewToolbar_Click() mnuViewToolbar.Checked = Not mnuViewToolbar.Checked tbToolBar.Visible = mnuViewToolbar.Checked End Sub

Private Sub mnuEditPasteSpecial_Click() 'ToDo: Add 'mnuEditPasteSpecial_Click' code. MsgBox "Add 'mnuEditPasteSpecial_Click' code." End Sub

Private Sub mnuEditPaste_Click() On Error Resume Next ' ActiveForm.rtfText.SelRTF = Clipboard.GetText

End Sub

Private Sub mnuEditCopy_Click() On Error Resume Next ' Clipboard.SetText ActiveForm.rtfText.SelRTF

End Sub

Private Sub mnuEditCut_Click() On Error Resume Next ' Clipboard.SetText ActiveForm.rtfText.SelRTF ' ActiveForm.rtfText.SelText = vbNullString

End Sub

Private Sub mnuEditUndo_Click() 'ToDo: Add 'mnuEditUndo_Click' code. MsgBox "Add 'mnuEditUndo_Click' code." End Sub

Private Sub mnuFileExit_Click() ilonl Dev%, 0 Close All End

227 End Sub

Private Sub mnuFileSend_Click() 'ToDo: Add 'mnuFileSend_Click' code. MsgBox "Add 'mnuFileSend_Click' code." End Sub

Private Sub mnuFilePrint_Click() On Error Resume Next If ActiveForm Is Nothing Then Exit Sub

End Sub

Private Sub mnuFilePrintPreview_Click() 'ToDo: Add 'mnuFilePrintPreview_Click' code. MsgBox "Add 'mnuFilePrintPreview_Click' code." End Sub

Private Sub mnuFilePageSetup_Click() On Error Resume Next With dlgCommonDialog .DialogTitle = "Page Setup" .CancelError = True .ShowPrinter End With

End Sub

Private Sub mnuFileProperties_Click() 'ToDo: Add 'mnuFileProperties_Click' code. MsgBox "Add 'mnuFileProperties_Click' code." End Sub

Private Sub mnuFileSaveAll_Click() 'ToDo: Add 'mnuFileSaveAll_Click' code. MsgBox "Add 'mnuFileSaveAll_Click' code." End Sub

Private Sub mnuFileSaveAs_Click() If ActiveForm.Caption <> "Viraj2007 Multimeter" Then ActiveForm.SaveAs Else

228 frmSR850.WindowState = 1 ActiveForm.SaveAs frmSR850.WindowState = 0 End If End Sub

Private Sub mnuFileSave_Click() If ActiveForm.Caption <> "Viraj2007 Multimeter" Then ActiveForm.Save Else frmSR850.WindowState = 1 ActiveForm.Save frmSR850.WindowState = 0 End If End Sub

Private Sub mnuFileClose_Click() 'ToDo: Add 'mnuFileClose_Click' code. MsgBox "Add 'mnuFileClose_Click' code." End Sub

Private Sub mnuFileOpen_Click() LoadNewDoc ActiveForm.Fopen End Sub

Private Sub mnuFileNew_Click() LoadNewDoc End Sub

Public Sub multioff() tbToolBar.Buttons.Item(5).Value = tbrUnpressed End Sub

Private Sub txtStart_Change() On Error Resume Next ActiveForm.SetScale Val(txtStart.Text), Val(txtStop.Text) End Sub

Private Sub txtStop_Change() On Error GoTo ee

ActiveForm.SetScale txtStart, txtStop ee: End Sub Sub UpdateDisp() Me.txtCurrPos = Format(gblCurWL&, "####.##") End Sub

Sub UpdateDispData(data As Single) Me.txtData = ChangeUnit(data) Me.txtCurrPos = gblCurWL& / 100 DoEvents End Sub

Sub UpdateMainScreen()

229 sbStatusBar.Panels(1).Text = "Current Grating :" & gblNGrtSelted& & " " & "Groove : " & gblCurGr& & " g/mm " & "Blaze : " & gblCurBl& & " nm" txtCurrPos.Text = gblCurWL& / 100 txtGrating.Text = gblNGrtSelted& txtFilter.Text = gblFilter% txtInputSlit.Text = gblS1% txtOutputSlit.Text = gblS2% If ShutOpen Then shpShutter.FillColor = &H8000000F lblShutter.Caption = "Open" Else shpShutter.FillColor = &H0 lblShutter.Caption = "Closed" End If

End Sub

Dim oBook As Excel.Workbook Dim oSheet As Excel.Worksheet Dim oChart As Excel.Chart Dim NoG As Long Dim DataBakGnd() As Variant Private FStep As Integer Private SStart As Single Private SStep As Single Private SStop As Single Private SLamda As Long Private LInten As Double 'Light Intensity W/cm² Dim n As Integer 'No of data points

Private Sub cmbDescription_Click() txtCellNo = cmbDescription.ListIndex + 1 DescripChange End Sub

Private Sub cmbDescription_DropDown() DescripChange End Sub

Private Sub cmbDescription_KeyPress(KeyAscii As Integer) If KeyAscii = 13 Then DescripChange End If End Sub

Private Sub cmbDescription_LostFocus() DescripChange

230 End Sub Sub DescripChange() cmbDescription.List(txtCellNo - 1) = cmbDescription.Text cmbDescription.ListIndex = txtCellNo - 1 With oSheet If NoG > 0 Then .Cells(3, (4 * NoG) - 2).Value = cmbDescription.List(NoG - 1) End If End With End Sub

Private Sub Form_Load() cmbDescription.List(0) = "Vbias= Rbias= Temp=" cmbDescription.ListIndex = 0 txtCellNo = cmbDescription.ListIndex + 1

OLE1.CreateEmbed "", "excel.chart" Set oBook = OLE1.object Set oChart = oBook.Charts(1) Set oSheet = oBook.Worksheets(1)

oSheet.Cells.Clear oChart.ChartType = xlXYScatterSmoothNoMarkers oChart.SetSourceData oSheet.Range("A13:B114"), xlColumns With oChart

.HasTitle = True .ChartTitle.AutoScaleFont = False .ChartTitle.Font.Size = 12 .ChartTitle.Text = "Spectral Response of the Sample" .HasLegend = True .Legend.Interior.ColorIndex = xlNone .Legend.Border.LineStyle = xlNone .Legend.AutoScaleFont = False .Legend.Font.Size = 8 .Legend.Left = 200 .Legend.Top = 50 .Axes(xlCategory, xlPrimary).HasTitle = True .Axes(xlCategory, xlPrimary).AxisTitle.AutoScaleFont = False .Axes(xlCategory, xlPrimary).AxisTitle.Font.Size = 12 .Axes(xlCategory, xlPrimary).AxisTitle.Characters.Text = "Wavelength(nm)" .Axes(xlValue, xlPrimary).HasTitle = True .Axes(xlValue, xlPrimary).AxisTitle.Characters.Text = "Sample Raw Response(V)" .Axes(xlValue, xlPrimary).AxisTitle.AutoScaleFont = False .Axes(xlValue, xlPrimary).AxisTitle.Font.Size = 12 End With With oChart.Axes(xlValue) .HasMajorGridlines = False .HasMinorGridlines = False .MajorTickMark = xlInside .MinorTickMark = xlNone .TickLabelPosition = xlNextToAxis .TickLabels.AutoScaleFont = False ' .TickLabels.NumberFormat = "0.00" .TickLabels.Font.Size = 12

231 .MinimumScale = 0 '.MaximumScale = 1

End With With oChart.Axes(xlCategory) .HasMajorGridlines = False .HasMinorGridlines = False .MajorTickMark = xlInside .MinorTickMark = xlNone .TickLabelPosition = xlNextToAxis .TickLabels.AutoScaleFont = False ' .TickLabels.NumberFormat = "0.00" .TickLabels.Font.Size = 12 .MinimumScale = fMainForm.txtStart .MaximumScale = fMainForm.txtStop

End With

oChart.PlotArea.Interior.ColorIndex = xlNone

OLE1.Visible = True ' OLE1.Close 'Deactivate the OLE container Application.Assistant.Visible = True If optAutoTrack(0).Value = True Then AutoTrack = True Else AutoTrack = False End If

End Sub

Private Sub Form_Resize() On Error Resume Next OLE1.Move 0, 1800, Me.ScaleWidth, Me.ScaleHeight - 2100 tbsGtoS.Top = 1440 tbsGtoS.Width = Me.ScaleWidth Frame2.Top = Me.ScaleHeight - 835 Frame2.Width = Me.ScaleWidth sldpos.Width = Frame2.Width - 300

End Sub

Sub Fopen() Dim sFile As String With CommonDialog .DialogTitle = "Open" .CancelError = False .Filter = "Excel File (*.xls)|*.xls" .DialogTitle = "Open IR Action Spectrum File" .ShowOpen If Len(.FileName) = 0 Then Exit Sub End If sFile = .FileName End With Caption = sFile

232 OLE1.CreateEmbed sFile, "excel.chart" Set oBook = OLE1.object Set oSheet = oBook.Worksheets(1)

With oSheet If Left(.Cells(1, 1).Value, 39) <> "Viraj2008 UV-VI-IR monochromator Data File" Then MsgBox "This is not a Viraj2008 UV-VI-IR monochromator Data file", vbOKOnly + vbInformation, "Invalied file format" Exit Sub End If Set oChart = oBook.Charts(1) c = 1 xx = .Cells(1, c).Value While xx <> "" c = c + 2 xx = .Cells(1, c).Value Wend End With NoG = (c - 1) / 2 For Z% = 1 To NoG cmbDescription.List(Z% - 1) = oSheet.Cells(3, 2 * Z%).Value Next Z% cmbDescription.AddItem "Sample No " & LTrim(Str(NoG + 1)) End Sub

Sub Save() Dim sFile As String If Left$(Caption, 13) = "Spectrum Book" Then On Error GoTo ErrHandler With CommonDialog .CancelError = True .Filter = "Excel File (*.xls)|*.xls" .DialogTitle = "Save IV Curve File" .Flags = cdlOFNOverwritePrompt .ShowSave If Len(.FileName) = 0 Then Exit Sub End If sFile = .FileName End With oBook.SaveCopyAs sFile Caption = sFile Else sFile = Caption oBook.SaveCopyAs sFile End If ErrHandler: Exit Sub End Sub

Sub SaveAs() Dim sFile As String On Error GoTo ErrHandler With CommonDialog .CancelError = True .Filter = "Excel File (*.xls)|*.xls"

233 .DialogTitle = "Save IV Curve File As" .Flags = cdlOFNOverwritePrompt .ShowSave If Len(.FileName) = 0 Then Exit Sub End If sFile = .FileName End With oBook.SaveCopyAs sFile Caption = sFile

ErrHandler: Exit Sub End Sub

Sub ScanSample(Min&, Step As Single, Max&, Delay As Integer, Avg As Integer) Dim TCDelay As Integer n = (Max& - Min&) / Step + 1 'total no of data

TCDelay = CInt(TimeConsSec * 1000) If PauseStop = 2 Then PauseStop = 0 Exit Sub End If PInc = 100 * Step / (Max - Min) sldpos.Value = 0 fMainForm.tbToolBar.Enabled = False MousePointer = 11

NoG = NoG + 1 Cn% = (NoG * 7) - 6 Rn% = 14

MsgWait "Please Wait... Moving to Starting Point" DoEvents MsgWait ""

GoToLamdaBG Min MsgWait "" With oSheet .Cells(1, Cn%).Value = "Viraj2008 UV-VI-IR monochromator Data File" .Cells(2, Cn%).Value = "Date/Time" .Cells(3, Cn%).Value = "Sample Description :" .Cells(3, Cn% + 1).Value = "Sample No " & NoG .Cells(4, Cn%).Value = "Chopping Frequency =" .Cells(5, Cn%).Value = "Time Constant =" .Cells(6, Cn%).Value = "Enterence Slit width (um)=" .Cells(7, Cn%).Value = "Exit Slit width (um)=" .Cells(8, Cn%).Value = "Delay before start averaging =" .Cells(9, Cn%).Value = "No of data to avarage =" .Cells(10, Cn%).Value = "Pre-amp gain =" .Cells(11, Cn%).Value = "Sample Area =" .Cells(12, Cn%).Value = "No of Data Points ="

.Cells(13, Cn%).Value = "Wavelength (nm)" .Cells(13, Cn% + 1).Value = "Sample Voltage Response(V)" .Cells(13, Cn% + 2).Value = "Gain Corrected Response(V)"

234 .Cells(13, Cn% + 3).Value = "Current Response(A)" .Cells(13, Cn% + 4).Value = "Light Intensity (W/cm²)" .Cells(13, Cn% + 5).Value = "sample Responsivity (V/W)" .Cells(13, Cn% + 6).Value = "sample Responsivity (A/W)" .Columns.AutoFit

End With

Wait Delay SetGain 'if overload detected decrease the sensitivity With oSheet wl% = gblCurWL& / 100 .Cells(Rn%, Cn%).Value = wl% .Cells(Rn%, Cn% + 1).Value = SR850AvgData(Avg, TCDelay)

f = "=R[13]C[" & Trim(Str(Cn%)) & "]/" & Trim(txtPAGain.Text) .Cells(Rn%, Cn% + 2).Formula = f 'Set Range0 = .Range("C14") Set Range1 = .Range(.Cells(Rn%, Cn% + 2), .Cells(Rn%, Cn% + 2)) Set Range2 = .Range(.Cells(Rn%, Cn% + 2), .Cells(Rn% + n, Cn% + 2)) 'Range0.Copy Destination:=Range1 Range1.AutoFill Destination:=Range2

'.Cells(Rn%, Cn% + 2).Value = .Cells(Rn%, Cn% + 1).Value * Val(txtPAGain.Text)

'.Cells(Rn%, Cn% + 3).Value = "?" .Cells(Rn%, Cn% + 4).Value = Intensity(wl%)

f = "=R[13]C[" & Trim(Str(Cn% + 1)) & "]/(R[13]C[" & Trim(Str(Cn% + 3)) & "]*" & Trim(txtArea.Text) & ")" .Cells(Rn%, Cn% + 5).FormulaR1C1 = f Set Range1 = .Range(.Cells(Rn%, Cn% + 5), .Cells(Rn%, Cn% + 5)) Set Range2 = .Range(.Cells(Rn%, Cn% + 5), .Cells(Rn% + n, Cn% + 5)) Range1.AutoFill Destination:=Range2

'.Cells(Rn%, Cn% + 5).Value = .Cells(Rn%, Cn% + 2).Value / (.Cells(Rn%, Cn% + 4).Value * Val(txtArea.Text))

End With With oChart .Axes(xlValue).MinimumScale = Auto If .Axes(xlCategory).MaximumScale < CInt(Max / 90) * 100 And Min < Max Then .Axes(xlCategory).MaximumScale = CInt(Max / 90) * 100 .Axes(xlCategory).MinimumScale = Min End If End With

If NoG > 1 Then oChart.SeriesCollection.NewSeries End If

With oSheet oChart.SeriesCollection(NoG).Name = oSheet.Range(oSheet.Cells(3, Cn% + 1), oSheet.Cells(3, Cn% + 1))

235 oChart.SeriesCollection(NoG).XValues = .Range(.Cells(14, Cn%), .Cells(14 + n, Cn%)) oChart.SeriesCollection(NoG).Values = .Range(.Cells(14, Cn% + 1), .Cells(14 + n, Cn% + 1)) End With

DoEvents

Rn% = Rn% + 1 sldpos.Value = PInc ' ***************************************************** For SLamda = Min + Step To Max Step Step If PauseStop = 2 Then Exit For End If GoToLamdaBG SLamda

With oSheet wl% = gblCurWL& / 100 .Cells(Rn%, Cn%).Value = wl% STime = Timer Wait Delay SetGain 'if overload detected decrease the sensitivity .Cells(Rn%, Cn% + 1).Value = SR850AvgData(Avg, TCDelay) lblRealDelay.Caption = Format((Timer - STime) * 1000, "#0000.00 ms") '.Cells(Rn%, Cn% + 2).Value = .Cells(Rn%, Cn% + 1).Value * Val(txtPAGain.Text) '.Cells(Rn%, Cn% + 3).Value = "?" .Cells(Rn%, Cn% + 4).Value = Intensity(wl%) '.Cells(Rn%, Cn% + 5).Value = .Cells(Rn%, Cn% + 2).Value / (.Cells(Rn%, Cn% + 4).Value * Val(txtArea.Text))

'LInten = LightInten(gblCurWL&) 'oSheet.Cells(Rn%, Cn% + 2).Value = LInten 'to calculate responsivity (A/W) 'oSheet.Cells(Rn%, Cn% + 3).Value = oSheet.Cells(Rn%, Cn% + 1).Value * 10000 / (LInten * txtArea.Text) 'to calculate IPCE% 'oSheet.Cells(Rn%, Cn% + 4).Value = oSheet.Cells(Rn%, Cn% + 3).Value * 125000 / gblCurWL& 'oChart.SeriesCollection(2 * NoG).XValues = .Range(.Cells(14, Cn%), .Cells(Rn%, Cn%)) 'oChart.SeriesCollection(2 * NoG).Values = .Range(.Cells(14, Cn% + 1), .Cells(Rn%, Cn% + 1)) 'oChart.SeriesCollection(NoG).XValues = .Range(.Cells(14, Cn%), .Cells(Rn%, Cn%)) 'oChart.SeriesCollection(NoG).Values = .Range(.Cells(14, Cn% + 1), .Cells(Rn%, Cn% + 1))

.Cells(12, Cn% + 1).Value = Rn% - 13 End With

Rn% = Rn% + 1 DoEvents If sldpos.Value + PInc < 101 Then sldpos.Value = sldpos.Value + PInc

236 End If WriteToSR850 "OUTP?3" fMainForm.UpdateDispData ReadSR850 While PauseStop = 1 DoEvents Wend Next SLamda ' Wend '*****************************************************

' oSheet.Cells(Rn%, Cn%).Value = 0 ' oSheet.Cells(Rn%, Cn% + 1).Value = 0 ' oChart.SeriesCollection(NoG).XValues = oSheet.Range(oSheet.Cells(14, Cn%), oSheet.Cells(Rn%, Cn%)) ' oChart.SeriesCollection(NoG).Values = oSheet.Range(oSheet.Cells(14, Cn% + 1), oSheet.Cells(Rn%, Cn% + 1))

With oSheet

.Cells(2, Cn% + 1).Value = Date & " at " & Time .Cells(3, Cn% + 1).Value = cmbDescription.List(NoG - 1)

WriteToSR850 "FREQ?" .Cells(4, Cn% + 1).Value = Format(ReadSR850, "#000.0")

.Cells(5, Cn% + 1).Value = TimeConstant .Cells(6, Cn% + 1).Value = fMainForm.txtInputSlit.Text .Cells(7, Cn% + 1).Value = fMainForm.txtOutputSlit.Text .Cells(8, Cn% + 1).Value = fMainForm.txtDelay.Text .Cells(9, Cn% + 1).Value = fMainForm.txtAvg.Text .Cells(10, Cn% + 1).Value = Me.txtPAGain.Text .Cells(11, Cn% + 1).Value = Me.txtArea.Text .Cells(12, Cn% + 1).Value = Rn% - 14 End With

'cmbDescription.List((2 * NoG) - 2) = "Sample No " & LTrim(Str(NoG))

cmbDescription.AddItem LTrim(cmbDescription.List(NoG - 1)) cmbDescription.ListIndex = NoG - 1

fMainForm.cmdPause.Enabled = False fMainForm.cmdStop.Enabled = False fMainForm.cmdPlay.Enabled = True

MousePointer = 0 If PauseStop = 0 Then sldpos.Value = sldpos.Max fMainForm.tbToolBar.Enabled = True

End Sub

Sub ScanABSBakGnd(Min&, Step As Single, Max&, Delay As Integer, Avg As Integer) ReDim DataBakGnd(1 To ((Max - Min) / Step) + 1, 1 To 2) Me.Caption = Me.Caption & "Scanning Background Spectra" Dim TCDelay As Integer TCDelay = CInt(TimeConsSec * 1000) MsgBox TCDelay If PauseStop = 2 Then

237 PauseStop = 0 Exit Sub End If PInc = 100 * Step / (Max - Min) sldpos.Value = 0 fMainForm.tbToolBar.Enabled = False MousePointer = 11

NoG = 1 Cn% = 1 Rn% = 14

MsgWait "Please Wait... Moving to Starting Point" DoEvents GoToLamdaBG Min MsgWait "" With oSheet .Cells(1, Cn%).Value = "Viraj2008 UV-VI-IR monochromator Data File" .Cells(2, Cn%).Value = "Date/Time" .Cells(3, Cn%).Value = "Absorption Background" .Cells(3, Cn% + 1).Value = "Sample No " & NoG .Cells(4, Cn%).Value = "Chopping Frequency =" .Cells(5, Cn%).Value = "Time Constant =" .Cells(6, Cn%).Value = "Enterence Slit width (um)=" .Cells(7, Cn%).Value = "Exit Slit width (um)=" .Cells(8, Cn%).Value = "Delay before start averaging =" .Cells(9, Cn%).Value = "No of data to avarage =" .Cells(10, Cn%).Value = "Pre-amp gain =" .Cells(11, Cn%).Value = "Sample Area =" .Cells(12, Cn%).Value = "No of Data Points ="

.Cells(13, Cn%).Value = "Wavelength (nm)" .Cells(13, Cn% + 1).Value = "Background spectra" .Columns.AutoFit

End With

Wait Delay SetGain 'if overload detected decrease the sensitivity

DataBakGnd(1, 1) = gblCurWL& / 100 DataBakGnd(1, 2) = SR850AvgData(Avg, TCDelay)

With oChart oSheet.Cells(Rn%, Cn%).Value = DataBakGnd(1, 1) oSheet.Cells(Rn%, Cn% + 1).Value = DataBakGnd(1, 2) .Axes(xlValue).MinimumScale = Auto If .Axes(xlCategory).MaximumScale < CInt(Max / 90) * 100 And Min < Max Then .Axes(xlCategory).MaximumScale = CInt(Max / 90) * 100 .Axes(xlCategory).MinimumScale = Min End If End With oChart.SeriesCollection(NoG).Name = oSheet.Range(oSheet.Cells(3, Cn% + 1), oSheet.Cells(3, Cn% + 1))

DoEvents

238

Rn% = Rn% + 1 sldpos.Value = PInc ' ***************************************************** For SLamda = Min + Step To Max Step Step If PauseStop = 2 Then Exit For End If GoToLamdaBG SLamda

With oSheet Wait Delay SetGain 'if overload detected decrease the sensitivity

DataBakGnd(Rn% - 13, 1) = gblCurWL& / 100 DataBakGnd(Rn% - 13, 2) = SR850AvgData(Avg, TCDelay) .Cells(Rn%, Cn%).Value = DataBakGnd(Rn% - 13, 1) .Cells(Rn%, Cn% + 1).Value = DataBakGnd(Rn% - 13, 2)

oChart.SeriesCollection(NoG).XValues = .Range(.Cells(14, Cn%), .Cells(Rn%, Cn%)) oChart.SeriesCollection(NoG).Values = .Range(.Cells(14, Cn% + 1), .Cells(Rn%, Cn% + 1)) .Cells(12, Cn% + 1).Value = Rn% - 13 End With Rn% = Rn% + 1 DoEvents If sldpos.Value + PInc < 101 Then sldpos.Value = sldpos.Value + PInc End If WriteToSR850 "OUTP?3" fMainForm.UpdateDispData ReadSR850 While PauseStop = 1 DoEvents Wend Next SLamda

With oSheet

.Cells(2, Cn% + 1).Value = Date & " at " & Time .Cells(3, Cn% + 1).Value = cmbDescription.List(NoG - 1)

WriteToSR850 "FREQ?" .Cells(4, Cn% + 1).Value = Format(ReadSR850, "#000.0")

'cmbDescription.List((2 * NoG) - 2) = "Sample No " & LTrim(Str(NoG))

239 cmbDescription.AddItem LTrim(cmbDescription.List(NoG - 1)) cmbDescription.ListIndex = NoG - 1

fMainForm.cmdPause.Enabled = False fMainForm.cmdStop.Enabled = False fMainForm.cmdPlay.Enabled = True

MousePointer = 0 If PauseStop = 0 Then sldpos.Value = sldpos.Max fMainForm.tbToolBar.Enabled = True

End Sub

Sub Calibrate(Min&, Step As Single, Max&, Delay As Integer, Avg As Integer) Dim SiData(200 To 1100) As Double Dim InGaAsData(500 To 2961) As Double Dim TCDelay As Integer n = (Max& - Min&) / Step + 1 'total no of data

txtPAGain.Text = "100 uA/V" MsgBox "Please set the current amp gain to 100 uA/V"

Me.Caption = Me.Caption & "Measuring output light intensity" TCDelay = CInt(TimeConsSec * 1000) If PauseStop = 2 Then PauseStop = 0 Exit Sub End If

PInc = 100 * Step / (Max - Min) sldpos.Value = 0 fMainForm.tbToolBar.Enabled = False MousePointer = 11

fn% = FreeFile() Open App.Path & "\SiSpeRes.dat" For Input As #fn% Input #fn%, a, b k% = 200 While Not EOF(fn%) Input #fn%, a, SiData(k%) k% = k% + 1 Wend Close #fn%

fn% = FreeFile() Open App.Path & "\InGaAsSpeRes.dat" For Input As #fn% Input #fn%, a, b k% = 500 While Not EOF(fn%) Input #fn%, a, InGaAsData(k%) k% = k% + 1 Wend Close #fn%

NoG = 1

240 Cn% = 1 Rn% = 14

MsgWait "Please Wait... Moving to Starting Point" DoEvents MsgWait "" GoToLamdaBG Min MsgWait "" With oSheet .Cells(1, Cn%).Value = "Viraj2008 UV-VI-IR Intensity calibration Data File" .Cells(2, Cn%).Value = "Date/Time" .Cells(3, Cn%).Value = "Calibration" .Cells(3, Cn% + 1).Value = "Sample No " & NoG .Cells(4, Cn%).Value = "Chopping Frequency =" .Cells(5, Cn%).Value = "Time Constant =" .Cells(6, Cn%).Value = "Enterence Slit width (um)=" .Cells(7, Cn%).Value = "Exit Slit width (um)=" .Cells(8, Cn%).Value = "Delay before start averaging =" .Cells(9, Cn%).Value = "No of data to avarage =" .Cells(10, Cn%).Value = "Pre-amp gain =" .Cells(11, Cn%).Value = "Sample Area =" .Cells(12, Cn%).Value = "No of Data Points ="

.Cells(13, Cn%).Value = "Wavelength (nm)" .Cells(13, Cn% + 1).Value = "Detector Voltage Response(V)" .Cells(13, Cn% + 2).Value = "Detector Current Response(A)" .Cells(13, Cn% + 3).Value = "Spectral Response (A/W)" .Cells(13, Cn% + 4).Value = "Light Power (W)" .Cells(13, Cn% + 5).Value = "Light Intensity (W/cm²)" .Columns.AutoFit

End With

Wait Delay SetGain 'if overload detected decrease the sensitivity

With oSheet wl% = gblCurWL& / 100 .Cells(Rn%, Cn%).Value = wl% .Cells(Rn%, Cn% + 1).Value = SR850AvgData(Avg, TCDelay) .Cells(Rn%, Cn% + 2).Value = .Cells(Rn%, Cn% + 1).Value * 0.0001 If gblDetectorSelted = 1 Then .Cells(Rn%, Cn% + 3).Value = SiData(wl%) DArea = 0.1296 'Si Detector area in cm² Else .Cells(Rn%, Cn% + 3).Value = InGaAsData(wl%) DArea = 0.007853981634 'InGaAs Detector area in cm² End If .Cells(Rn%, Cn% + 4).Value = .Cells(Rn%, Cn% + 2).Value / .Cells(Rn%, Cn% + 3).Value Intensity(wl%) = .Cells(Rn%, Cn% + 4).Value / DArea .Cells(Rn%, Cn% + 5).Value = Intensity(wl%) End With With oChart .Axes(xlValue).MinimumScale = Auto

241 If .Axes(xlCategory).MaximumScale < CInt(Max / 90) * 100 And Min < Max Then .Axes(xlCategory).MaximumScale = CInt(Max / 90) * 100 .Axes(xlCategory).MinimumScale = Min End If End With With oSheet oChart.SeriesCollection(NoG).Name = oSheet.Range(oSheet.Cells(3, Cn% + 1), oSheet.Cells(3, Cn% + 1)) oChart.SeriesCollection(NoG).XValues = .Range(.Cells(14, Cn%), .Cells(14 + n, Cn%)) oChart.SeriesCollection(NoG).Values = .Range(.Cells(14, Cn% + 1), .Cells(14 + n, Cn% + 1)) End With DoEvents

Rn% = Rn% + 1 sldpos.Value = PInc ' ***************************************************** For SLamda = Min + Step To Max Step Step If PauseStop = 2 Then Exit For End If GoToLamdaBG SLamda

With oSheet Wait Delay SetGain 'if overload detected decrease the sensitivity wl% = Int(gblCurWL& / 100) .Cells(Rn%, Cn%).Value = gblCurWL& / 100 .Cells(Rn%, Cn% + 1).Value = SR850AvgData(Avg, TCDelay) .Cells(Rn%, Cn% + 2).Value = .Cells(Rn%, Cn% + 1).Value * 0.0001 If gblDetectorSelted = 1 Then .Cells(Rn%, Cn% + 3).Value = SiData(wl%) DArea = 0.1296 'Si Detector area in cm² Else .Cells(Rn%, Cn% + 3).Value = InGaAsData(wl%) DArea = 0.007853981634 'InGaAs Detector area in cm² End If .Cells(Rn%, Cn% + 4).Value = .Cells(Rn%, Cn% + 2).Value / .Cells(Rn%, Cn% + 3).Value Intensity(wl%) = .Cells(Rn%, Cn% + 4).Value / DArea .Cells(Rn%, Cn% + 5).Value = Intensity(wl%)

'oChart.SeriesCollection(NoG).XValues = .Range(.Cells(14, Cn%), .Cells(Rn%, Cn%)) 'oChart.SeriesCollection(NoG).Values = .Range(.Cells(14, Cn% + 1), .Cells(Rn%, Cn% + 1)) .Cells(12, Cn% + 1).Value = Rn% - 13

End With

Rn% = Rn% + 1 DoEvents If sldpos.Value + PInc < 101 Then sldpos.Value = sldpos.Value + PInc End If

242 WriteToSR850 "OUTP?3" fMainForm.UpdateDispData ReadSR850 While PauseStop = 1 DoEvents Wend Next SLamda

With oSheet

.Cells(2, Cn% + 1).Value = Date & " at " & Time .Cells(3, Cn% + 1).Value = cmbDescription.List(NoG - 1)

WriteToSR850 "FREQ?" .Cells(4, Cn% + 1).Value = Format(ReadSR850, "#000.0")

'cmbDescription.List((2 * NoG) - 2) = "Sample No " & LTrim(Str(NoG))

cmbDescription.AddItem LTrim(cmbDescription.List(NoG - 1)) cmbDescription.ListIndex = NoG - 1

fMainForm.cmdPause.Enabled = False fMainForm.cmdStop.Enabled = False fMainForm.cmdPlay.Enabled = True

MousePointer = 0 If PauseStop = 0 Then sldpos.Value = sldpos.Max fMainForm.tbToolBar.Enabled = True

End Sub

Private Sub optAutoTrack_Click(Index As Integer) If Index = 0 Then AutoTrack = True Else AutoTrack = False End If End Sub

Private Sub tbsGtoS_Click()

Select Case tbsGtoS.SelectedItem.Index Case 1 With oChart .ChartTitle.Text = "Raw Response of the Sample" .Axes(xlValue, xlPrimary).AxisTitle.Characters.Text = "Sample Raw Response(V)"

243 End With

With oSheet If .Cells(3, 1).Value = "Calibration" Then oChart.SeriesCollection(1).Values = .Range(.Cells(14, 2), .Cells(14 + n, 2)) Else For k = 1 To NoG cc% = (k * 7) - 6 oChart.SeriesCollection(k).Values = .Range(.Cells(14, cc% + 1), .Cells(14 + n, cc% + 1)) Next k End If End With Case 2 With oChart .ChartTitle.Text = "Responsivity of the Sample" .Axes(xlValue, xlPrimary).AxisTitle.Characters.Text = "Responsivity (V/W)" End With

With oSheet If oSheet.Cells(3, 1).Value = "Calibration" Then oChart.SeriesCollection(1).Values = .Range(.Cells(14, 4), .Cells(14 + n, 4)) Else For k = 1 To NoG cc% = (k * 7) - 6 oChart.SeriesCollection(k).Values = .Range(.Cells(14, cc% + 5), .Cells(14 + n, cc% + 5)) Next k End If End With

Case 3 With oChart .ChartTitle.Text = "Monochoromator Light Intensity" .Axes(xlValue, xlPrimary).AxisTitle.Characters.Text = "Light Intensity (W/cm²)" End With

With oSheet If oSheet.Cells(3, 1).Value = "Calibration" Then oChart.SeriesCollection(1).Values = .Range(.Cells(14, 6), .Cells(14 + n, 6)) Else For k = 1 To NoG cc% = (k * 7) - 6 oChart.SeriesCollection(k).Values = .Range(.Cells(14, cc% + 4), .Cells(14 + n, cc% + 4)) Next k End If End With

End Select

End Sub

244

Private Sub txtCellNo_Click() CommonDialog.ShowColor If NoG > 0 Then With oChart.SeriesCollection(Val(txtCellNo)) .Border.Color = CommonDialog.Color .MarkerBackgroundColor = CommonDialog.Color .MarkerForegroundColor = 0 .MarkerSize = 4 End With End If End Sub

Sub SetScale(Min As Single, Max As Single) oChart.Axes(xlCategory).MinimumScale = Min oChart.Axes(xlCategory).MaximumScale = Max End Sub

*********************************************************************** frmMonitor.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Dim nn As Integer Private Sub chkOnOff_Click() 'On Error Resume Next If chkOnOff.Value Then

WriteToSR850 "SENS?" CmbGain.ListIndex = Int(ReadSR850())

WriteToSR850 "OFLT?" cmbTimeConst.ListIndex = Int(ReadSR850())

cmbGrating.ListIndex = gblNGrtSelted& - 1 txtWLength.Text = gblCurWL& / 100 Option1(gblFilter% - 1).Value = True txtSlit1.Text = gblS1% txtSlit2.Text = gblS2% cmdAutoGain.Enabled = False cmdAutoReserve.Enabled = False DoEvents Timer1.Enabled = True

Else Timer1.Enabled = False cmdAutoGain.Enabled = True cmdAutoReserve.Enabled = True fMainForm.optMode(1).Value = True End If End Sub

Private Sub CmbGain_Click() WriteToSR850 "SENS" & Trim(Str(CmbGain.ListIndex))

245 End Sub

Private Sub cmbGrating_Click() txtMsg.Text = "Please Wait... Changing the Grating" txtMsg.Visible = True DoEvents Status% = DKGrtsel%(cmbGrating.ListIndex + 1, fMainForm.comComm1, 500) txtMsg.Visible = False

If Status% < 128 Then gblNGrtSelted& = cmbGrating.ListIndex + 1 Else MsgBox "An error has occurred !", MB_ICONSTOP End If fMainForm.UpdateMainScreen End Sub

Private Sub cmbTimeConst_Click() WriteToSR850 "OFLT" & Trim(Str(cmbTimeConst.ListIndex)) End Sub

Private Sub cmdAutoGain_Click() WriteToSR850 "AGAN" End Sub

Private Sub cmdAutoPhase_Click() WriteToSR850 "APHS" End Sub

Private Sub cmdAutoReserve_Click() WriteToSR850 "ARSV" End Sub

Private Sub cmdAutoScale_Click() WriteToSR850 "ASCL" End Sub

Private Sub cmdClsScreen_Click() ClsScreen End Sub

Private Sub cmdGo_Click() txtMsg.Text = "Please Wait... Changing the Wavelength" txtMsg.Visible = True DoEvents GoToLamdaCG txtWLength.Text txtMsg.Visible = False End Sub

Private Sub cmdGotoScanMode_Click() Me.Visible = False fMainForm.optMode(1).Value = True End Sub

Private Sub cmdGoZero_Click() txtMsg.Text = "Please Wait... Changing the Wavelength"

246 txtMsg.Visible = True DoEvents GoToLamdaCG 0 txtMsg.Visible = False End Sub

Private Sub cmdMotPow_Click() If MotPowON Then MotorPower "OFF" shpMPwLED.FillColor = &H0 Else MotorPower "ON" shpMPwLED.FillColor = &HFF& txtMsg.Text = "Please wait Initilizing Stepper Motors" txtMsg.Visible = True DoEvents InitializeMM InitializeDM txtMsg.Visible = False End If End Sub

Private Sub cmdRefRatSet_Click() Timer1.Interval = Val(txtRefrate.Text) End Sub

Private Sub cmdSet_Click() SetSlt 2, Val(txtSlit2.Text) On Error GoTo cmdCanOKErr

txtMsg.Text = "Please Wait... Changing the Slit Width" txtMsg.Visible = True DoEvents Status% = DKSltAdjCal%(31, Val(txtSlit1.Text), fMainForm.comComm1, 500) If Status% > 127 Then GoTo cmdCanOKErr gblS1% = Val(txtSlit1.Text) ' S1 adjustment. gblOkCancel% = IDOK

Status% = DKSltAdjCal%(32, Val(txtSlit2.Text), fMainForm.comComm1, 500) If Status% > 127 Then GoTo cmdCanOKErr gblS2% = Val(txtSlit2.Text) ' S2 adjustment. gblOkCancel% = IDOK

fMainForm.UpdateMainScreen txtMsg.Visible = False Exit Sub cmdCanOKErr: MsgBox "Error code is : " & Err, MB_ICONEXCLAMATION

End Sub

Private Sub Form_Activate() ClsScreen optLamp(gblLightSelted - 1).Value = True optDetector(gblDetectorSelted - 1).Value = True WriteToSR850 "SENS?"

247 CmbGain.ListIndex = Int(ReadSR850())

WriteToSR850 "OFLT?" cmbTimeConst.ListIndex = Int(ReadSR850())

cmbGrating.ListIndex = gblNGrtSelted& - 1 txtWLength.Text = gblCurWL& / 100 Option1(gblFilter% - 1).Value = True txtSlit1.Text = gblS1% txtSlit2.Text = gblS2%

End Sub

Private Sub Form_Resize() On Error Resume Next MSChart1.Move 1080, -140, Me.ScaleWidth - 900, Me.ScaleHeight - 1600 Frame1.Top = Me.ScaleHeight - 2000 Frame1.Left = 1350 Frame5.Height = Me.ScaleHeight - 60 txtMsg.Top = MSChart1.Height / 2 - 262 txtMsg.Left = Me.ScaleWidth / 2 - 1767 End Sub

Private Sub Form_Unload(Cancel As Integer) Timer1.Enabled = False fMainForm.optMode(1).Value = True 'SaveFormData Me, App.Path & "\Settings_Monitor.dat" End Sub

Private Sub optDetector_Click(Index As Integer) txtMsg.Text = "Please wait... Changing the Detector" txtMsg.Visible = True DoEvents RunDM frmStpMotSet.txtDetStp(Index) gblDetectorSelted = Index + 1 txtMsg.Visible = False MsgBox "Please connect the Detector " & Trim(Str(Index + 1)) & " to the pre-amp" End Sub

Private Sub Option1_Click(Index As Integer) On Error GoTo cmdCanOKErr txtMsg.Text = "Please wait... Changing to Filter # " & Index + 1 txtMsg.Visible = True DoEvents

248

Status% = DKFilter%(Index + 1, fMainForm.comComm1, 5) '5: 5s Timeout%

If Status% < 128 Then gblFilter% = Index + 1 gblOkCancel% = IDOK fMainForm.UpdateMainScreen txtMsg.Visible = False Exit Sub cmdCanOKErr: MsgBox "Error code is : " & Err, MB_ICONEXCLAMATION

End Sub

Private Sub optLamp_Click(Index As Integer) txtMsg.Text = "Please wait... Changing the light Source" txtMsg.Visible = True DoEvents RunMM frmStpMotSet.txtLmpStp(Index) gblLightSelted = Index + 1 txtMsg.Visible = False End Sub

Private Sub Timer1_Timer() Dim Dt As Single Dim SB As Byte 'Static nn As Integer If nn >= 200 Or nn < 1 Then nn = 1 Dt = SR850Data txtData.Text = ChangeUnit(Dt) With MSChart1 .Row = nn .Column = 1 .data = Dt nn = nn + 1 For jj = nn To 200 .Row = jj .Column = 1 .data = Dt Next jj

End With WriteToSR850 "LIAS?" SB = ReadSR850 For k = 0 To 2 If (SB And 2 ^ k) = 2 ^ k Then lblLED(k).Visible = True Else lblLED(k).Visible = False Next k End Sub

Private Sub ClsScreen() For k = 1 To 200 With MSChart1 .Row = k .Column = 1

249 .data = " "

End With Next k nn = 1 End Sub

Sub SetSlt(SlitNo As Integer, SlitWidth As Integer) End Sub

*********************************************************************** frmAdvSetup.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private Sub cmdClose_Click() Me.Visible = False End Sub

Private Sub cmdRstDft_Click() ReadFormData Me, App.Path & "\Settings_Dflt_AdvSetup.dat" SaveFormData Me, App.Path & "\Settings_AdvSetup.dat" End Sub

Private Sub cmdSave_Click() nl = Chr(10) & Chr(13) cho = MsgBox("You are attempting to change an important system setting." & nl & "This may result incorect spectral measurment data." & nl & "Do you really want save these new settings", vbExclamation + vbYesNo, "!!! WARNING !!!") If cho = 6 Then SaveFormData Me, App.Path & "\Settings_AdvSetup.dat" End If End Sub

Private Sub Form_Load() ReadFormData Me, App.Path & "\Settings_AdvSetup.dat" End Sub

Private Sub hscPic_Change() imgPic.Left = -hscPic.Value End Sub

Private Sub smdStMoSett_Click() frmStpMotSet.Visible = True End Sub

*********************************************************************** frmChopper.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

250

Private MidFre As Single

Private Sub cmdChFre_Click(Index As Integer)

End Sub

Private Sub cmdOk_Click()

Unload Me End Sub

Private Sub cmdSetFre_Click() Me.MousePointer = 11 OutV = Val(txtChoFre.Text) / 33 WriteToSR850 "AUXV1," & Trim(Str(OutV))

While Abs(Val(txtChoFre.Text) - Val(lblDispChopperFre.Caption)) > 1 If Val(txtChoFre.Text) > Val(lblDispChopperFre.Caption) Then OutV = OutV + 0.05 WriteToSR850 "AUXV1," & Trim(Str(OutV)) Wait 2000 WriteToSR850 "FREQ?" lblDispChopperFre.Caption = Format(ReadSR850, "#000.00 Hz") Else OutV = OutV - 0.048 WriteToSR850 "AUXV1," & Trim(Str(OutV)) Wait 2000 WriteToSR850 "FREQ?" lblDispChopperFre.Caption = Format(ReadSR850, "#000.00 Hz") End If DoEvents Wend

While Abs(Val(txtChoFre.Text) - Val(lblDispChopperFre.Caption)) > 0.1 If Val(txtChoFre.Text) > Val(lblDispChopperFre.Caption) Then OutV = OutV + 0.01 WriteToSR850 "AUXV1," & Trim(Str(OutV)) Wait 2000 WriteToSR850 "FREQ?" lblDispChopperFre.Caption = Format(ReadSR850, "#000.00 Hz") Else OutV = OutV - 0.009 WriteToSR850 "AUXV1," & Trim(Str(OutV)) Wait 2000 WriteToSR850 "FREQ?" lblDispChopperFre.Caption = Format(ReadSR850, "#000.00 Hz") End If DoEvents Wend While Abs(Val(txtChoFre.Text) - Val(lblDispChopperFre.Caption)) > 0.04 If Val(txtChoFre.Text) > Val(lblDispChopperFre.Caption) Then OutV = OutV + 0.001 WriteToSR850 "AUXV1," & Trim(Str(OutV)) Wait 2000 WriteToSR850 "FREQ?" lblDispChopperFre.Caption = Format(ReadSR850, "#000.00 Hz")

251 Else OutV = OutV - 0.001 WriteToSR850 "AUXV1," & Trim(Str(OutV)) Wait 2000 WriteToSR850 "FREQ?" lblDispChopperFre.Caption = Format(ReadSR850, "#000.00 Hz") End If DoEvents Wend Me.MousePointer = 0

End Sub

Private Sub Form_Load() WriteToSR850 "AUXM1,0" WriteToSR850 "FREQ?" lblDispChopperFre.Caption = Format(ReadSR850, "#000.00 Hz") txtChoFre.Text = lblDispChopperFre.Caption End Sub

Private Sub optChoFre_Click(Index As Integer) Select Case Index

Case 0 WriteToSR850 "AUXV1,0.28" lblDispChopperFre.Caption = Format(7, "#000.00 Hz") Case 1 WriteToSR850 "AUXV1,0.46" lblDispChopperFre.Caption = Format(13, "#000.00 Hz") Case 2 WriteToSR850 "AUXV1,0.58" lblDispChopperFre.Caption = Format(17, "#000.00 Hz") Case 3 WriteToSR850 "AUXV1,0.86" lblDispChopperFre.Caption = Format(27, "#000.00 Hz") Case 4 WriteToSR850 "AUXV1,1.15" lblDispChopperFre.Caption = Format(37, "#000.00 Hz") Case 5 WriteToSR850 "AUXV1,2.135" lblDispChopperFre.Caption = Format(71, "#000.00 Hz")

End Select

End Sub

*********************************************************************** frmStpMotSet.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private Sub cmdDDec_Click(Index As Integer) txtDetStp(Index).Text = Val(txtDetStp(Index).Text) - 1 RunDM Val(txtDetStp(Index).Text)

252 End Sub

Private Sub cmdDec_Click(Index As Integer) txtLmpStp(Index).Text = Val(txtLmpStp(Index).Text) - 1 RunMM Val(txtLmpStp(Index).Text) End Sub

Private Sub cmdDInc_Click(Index As Integer) txtDetStp(Index).Text = Val(txtDetStp(Index).Text) + 1 RunDM Val(txtDetStp(Index).Text) End Sub

Private Sub cmdDSet_Click(Index As Integer) RunDM Val(txtDetStp(Index).Text) End Sub

Private Sub cmdExit_Click() Me.Visible = False End Sub

Private Sub cmdInc_Click(Index As Integer) txtLmpStp(Index).Text = Val(txtLmpStp(Index).Text) + 1 RunMM Val(txtLmpStp(Index).Text) End Sub

Private Sub cmdRestDflt_Click() ReadFormData Me, App.Path & "\Settings_Dflt_StpMotSet.dat" SaveFormData Me, App.Path & "\Settings_StpMotSet.dat" End Sub

Private Sub cmdSave_Click() nl = Chr(10) & Chr(13) cho = MsgBox("You are attempting to change an important system setting." & nl & "This may result incorect Lamp and Detector positions" & nl & "Do you really want save these new settings", vbExclamation + vbYesNo, "!!! WARNING !!!") If cho = 6 Then SaveFormData Me, App.Path & "\Settings_StpMotSet.dat" End If

End Sub

Private Sub cmdSet_Click(Index As Integer) RunMM Val(txtLmpStp(Index).Text) End Sub

Private Sub Form_Load() ReadFormData Me, App.Path & "\Settings_StpMotSet.dat" End Sub

Private Sub Label11_Click()

End Sub

*********************************************************************** frmSR850.frm

253 *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private MP As String Private Sub CmbGain_Click() WriteToSR850 "SENS" & Trim(Str(CmbGain.ListIndex)) End Sub

Private Sub cmbTimeConst_Click() WriteToSR850 "OFLT" & Trim(Str(cmbTimeConst.ListIndex)) End Sub

Private Sub cmdAutoGain_Click() WriteToSR850 "AGAN" 'Wait 5000 'WriteToSR850 "SENS ?" 'CmbGain.ListIndex = ReadSR850 'WriteToSR850 "OFLT ?" 'cmbTimeConst.ListIndex = ReadSR850

End Sub

Private Sub cmdAutoPhase_Click() WriteToSR850 "APHS" End Sub

Private Sub cmdAutoRese_Click() WriteToSR850 "ARSV" End Sub

Private Sub cmdAutoScale_Click() WriteToSR850 "ASCL" End Sub

Private Sub cmdAUX2_Click() If Me.lblAUX2.BackColor = &H0& Then Me.lblAUX2.BackColor = &HFF00& Me.txtAUX2.Enabled = True Me.sldAUX2.Enabled = True WriteToSR850 "AUXM2,0 " WriteToSR850 "AUXV2,0.000 " Else Me.lblAUX2.BackColor = &H0& WriteToSR850 "AUXV2,0.000 " Me.txtAUX2 = "0.000" Me.txtAUX2.Enabled = False Me.sldAUX2.Enabled = False End If

End Sub

Private Sub cmdAUX3_Click() If Me.lblAUX3.BackColor = &H0& Then Me.lblAUX3.BackColor = &HFF00& Me.txtAUX3.Enabled = True

254 Me.sldAUX3.Enabled = True WriteToSR850 "AUXM3,0 " WriteToSR850 "AUXV3,0.000 " Else Me.lblAUX3.BackColor = &H0& WriteToSR850 "AUXV3,0.000 " Me.txtAUX3 = "0.000" Me.txtAUX3.Enabled = False Me.sldAUX3.Enabled = False End If End Sub

Private Sub cmdAUX4_Click() If Me.lblAUX4.BackColor = &H0& Then Me.lblAUX4.BackColor = &HFF00& Me.txtAUX4.Enabled = True Me.sldAUX4.Enabled = True WriteToSR850 "AUXM4,0" WriteToSR850 "AUXV4,0.000" Else Me.lblAUX4.BackColor = &H0& WriteToSR850 "AUXV4,0.000" Me.txtAUX4 = "0.000" Me.txtAUX4.Enabled = False Me.sldAUX4.Enabled = False End If End Sub

Private Sub cmdIMode_Click() WriteToSR850 "ISRC2" MP = "A" End Sub

Private Sub cmdOk_Click() Me.Timer1.Enabled = False Unload Me End Sub

Private Sub cmdRefresh_Click() If Me.cmdRefresh.Caption = "Refresh ON" Then Me.cmdRefresh.Caption = "Refresh OFF" Timer1.Enabled = True Else Me.cmdRefresh.Caption = "Refresh ON" Timer1.Enabled = False End If End Sub

Private Sub cmdVMode_Click() WriteToSR850 "ISRC0" MP = "V" End Sub

Private Sub Form_Load() WriteToSR850 "RMOD1" WriteToSR850 "SENS?" CmbGain.ListIndex = ReadSR850

255 WriteToSR850 "OFLT?" cmbTimeConst.ListIndex = ReadSR850 WriteToSR850 "AUXM2,0"

WriteToSR850 "AUXV?2" Me.txtAUX2 = ReadSR850 If Me.txtAUX2 <> 0 Then Me.txtAUX2.Enabled = True Me.sldAUX2.Enabled = True Me.lblAUX2.BackColor = &HFF00& End If

WriteToSR850 "AUXV?3" Me.txtAUX3 = ReadSR850 If Me.txtAUX3 <> 0 Then Me.txtAUX3.Enabled = True Me.sldAUX3.Enabled = True Me.lblAUX3.BackColor = &HFF00& End If

WriteToSR850 "AUXV?4" Me.txtAUX4 = ReadSR850 If Me.txtAUX4 <> 0 Then Me.txtAUX4.Enabled = True Me.sldAUX4.Enabled = True Me.lblAUX4.BackColor = &HFF00& End If WriteToSR850 "ISRC?" If ReadSR850 = 2 Then MP = "A" Else MP = "V"

Timer1.Enabled = True End Sub

Private Sub Form_Unload(Cancel As Integer) Timer1.Enabled = False End Sub

Private Sub sldAUX2_Click() Me.txtAUX2 = Me.sldAUX2.Value / 1000 End Sub

Private Sub sldAUX3_Click() Me.txtAUX3 = Me.sldAUX3.Value / 1000 End Sub

Private Sub sldAUX4_Click() Me.txtAUX4 = Me.sldAUX4.Value / 1000 End Sub

Private Sub Timer1_Timer() WriteToSR850 "OUTP?3" Me.lblR = ChangeUnit(ReadSR850) & MP WriteToSR850 "OUTP?1" Me.lblX = ChangeUnit(ReadSR850) & MP WriteToSR850 "OUTP?2" Me.lblY = ChangeUnit(ReadSR850) & MP WriteToSR850 "OUTP?4"

256 Me.lblTheeta = Format(ReadSR850, "000.00") End Sub

Private Sub txtAUX2_Change() If Val(txtAUX2.Text) > 10.5 Then txtAUX2.Text = 10.5 If Val(txtAUX2.Text) < -10.5 Then txtAUX2.Text = -10.5 Me.sldAUX2.Value = Val(Me.txtAUX2) * 1000 WriteToSR850 "AUXV2," & Me.txtAUX2 End Sub

Private Sub txtAUX3_Change() If Val(txtAUX3.Text) > 10.5 Then txtAUX3.Text = 10.5 If Val(txtAUX3.Text) < -10.5 Then txtAUX3.Text = -10.5 Me.sldAUX3.Value = Val(Me.txtAUX3) * 1000 WriteToSR850 "AUXV3," & Me.txtAUX3 End Sub

Private Sub txtAUX4_Change() If Val(txtAUX4.Text) > 10.5 Then txtAUX4.Text = 10.5 If Val(txtAUX4.Text) < -10.5 Then txtAUX4.Text = -10.5 Me.sldAUX4.Value = Val(Me.txtAUX4) * 1000 WriteToSR850 "AUXV4," & Trim(Me.txtAUX4) End Sub

257 B.3 Noise spectrum analyzer software

The detector noise characterization system is controlled using an in-house software package developed with Microsoft Visual Basic. The system is based on an SR785, dual channel, Fourier transform, dynamic signal analyzer and SR550, low noise preamplifier. The software uses the

GPIB interface to communicate with the instrument. The software capabilities include: control all the front panel functions (except power on) through the software, read data from the SR785, record data in an embedded Microsoft Excel workbook, with single channel or dual channel modes.

258 B.3.1 Instrument configuration of the noise measurement setup

Shielding metal Box

Dewar SR785 dual channel Fourier transform dynamic signal analyzer SR550 low noise pre-Amp Sample RB

Pre-Amp Bias Box

259 B.3.2 User interfaces

Figure B.22 The main user interface for the noise spectrum analyzer software showing real experimental data taken from the samples.

260

Figure B.23 Spectrum analyzer control panel. On screen buttons allow the user to change the parameters remotely without using the instrument front panel buttons.

261 B.3.3 Source code

*********************************************************************** SR785_GPIB.bas *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Attribute VB_Name = "SR785_GPIB" Const BDINDEX = 0 ' Board Index Const PRIMARY_ADDR_OF_DMM = 10 ' Primary address of device Const NO_SECONDARY_ADDR = 0 ' Secondary address of device Const TIMEOUT = T10s ' Timeout value = 10 seconds Const EOTMODE = 1 ' Enable the END message Const EOSMODE = 0 ' Disable the EOS mode

Const ARRAYSIZE = 1024 ' Size of read buffer

Dim Msg As String * 100 Dim Dev As Integer Dim ErrorMnemonic Dim ValueStr As String * ARRAYSIZE Dim data As String * 13700 Dim Response As Integer

'To Queries SR785 settings Function QueriesSR785(CmdString As String) ilwrt Dev%, CmdString, Len(CmdString) If (ibsta And EERR) Then Call GPIBCleanup("Unable to write to device") End If

ilrd Dev%, ValueStr, Len(ValueStr) If (ibsta And EERR) Then Call GPIBCleanup("Unable to read from device") End If QueriesSR785 = Val(Left$(ValueStr, ibcntl - 1))

End Function

'To write command to SR785 Sub WriteToSR785(CommandString As String) ilwrt Dev%, CommandString, Len(CommandString) If (ibsta And EERR) Then Call GPIBCleanup("Unable to write to device") End If End Sub

'To read Data from SR785 Function ReadSR785() As String ilrd Dev%, data, Len(data) 'len(ValueStr) If (ibsta And EERR) Then Call GPIBCleanup("Unable to read from device") End If ReadSR785 = Trim(data)

262 End Function

Sub InitializeGPIB() Dev% = ildev(BDINDEX, PRIMARY_ADDR_OF_DMM, NO_SECONDARY_ADDR, _ TIMEOUT, EOTMODE, EOSMODE) If (ibsta And EERR) Then ErrMsg = "Unable to open device" & Chr(13) & "ibsta = &H" & _ Chr(13) & Hex(ibsta) & "iberr = " & iberr MsgBox ErrMsg, vbCritical, "Error" End End If ' The application resets the GPIB portion of the device by calling ' ilclr. ilclr Dev% If (ibsta And EERR) Then Call GPIBCleanup("Unable to clear device") End If

End Sub

Sub GPIBCleanup(Msg$)

ErrorMnemonic = Array("EDVR", "ECIC", "ENOL", "EADR", "EARG", _ "ESAC", "EABO", "ENEB", "EDMA", "", _ "EOIP", "ECAP", "EFSO", "", "EBUS", _ "ESTB", "ESRQ", "", "", "", "ETAB")

ErrMsg$ = Msg$ & Chr(13) & "ibsta = &H" & Hex(ibsta) & Chr(13) _ & "iberr = " & iberr & " <" & ErrorMnemonic(iberr) & ">" MsgBox ErrMsg$, vbCritical, "Error" ilonl Dev%, 0

End Sub

Sub ResetSR785ToNoise()

If Channel = 0 Then WriteToSR785 "DFMT 0" 'Set display format to single WriteToSR785 "MEAS 0,2" 'Set measurment Power Spectrum 1 Else WriteToSR785 "DFMT 1" 'Set display format to Dual WriteToSR785 "MEAS 0,2" 'Set measurment Power Spectrum 1 WriteToSR785 "MEAS 1,3" 'Set measurment Power Spectrum 2 End If

WriteToSR785 "LINK 1" 'Set Analyzer configeration to Dual channel WriteToSR785 "ACDT 0" 'Set Active display to A WriteToSR785 "MGRP " & Channel & " ,0" 'Set measurment group to FFT WriteToSR785 "VIEW " & Channel & " ,0" 'Set View of display A to Log magnitude WriteToSR785 "UNDB " & Channel & " ,0" 'Set dB units Off

263 WriteToSR785 "UNPK " & Channel & " ,2" 'Set pk units to rms WriteToSR785 "PSDU " & Channel & " ,1" 'Set psd units ON WriteToSR785 "XAXS " & Channel & " ,1" 'Set X axis scale type to Logarthmic WriteToSR785 "ISRC 0" 'Set Input source Analog WriteToSR785 "I1MD 0" 'Set Channel 1 input mode single-ended WriteToSR785 "I1GD 0" 'Set Channel 1 Input Grounding to Float WriteToSR785 "I1CP 1" 'Set Channel 1 Input Coupling to AC WriteToSR785 "I1AR 1" 'Set Channel 1 Auto range mode Tracking

WriteToSR785 "I2MD 0" 'Set Channel 2 input mode single-ended WriteToSR785 "I2GD 0" 'Set Channel 2 Input Grounding to Float WriteToSR785 "I2CP 1" 'Set Channel 2 Input Coupling to AC WriteToSR785 "I2AR 1" 'Set Channel 2 Auto range mode Tracking

WriteToSR785 "IAOM 0" 'Set Auto offset Off WriteToSR785 "FAVM " & Channel & " ,2" 'Set type of averaging RMS WriteToSR785 "FAVT " & Channel & " ,1" 'Set Averaging type Exponential/Continuous WriteToSR785 "FAVN " & Channel & " ,500" 'Set Number of averages 500

WriteToSR785 "PDST 3" 'Set the Print/Plot/Dump destination GPIB Port WriteToSR785 "PCIC 0" 'Set the GPIB control mode Host

WriteToSR785 "FLIN " & Channel & " ,3" 'Set Resolution to 800

WriteToSR785 "KEYP 37" 'press Auto scale A

WriteToSR785 "KEYP 17" 'press Start

If QueriesSR785("A1RG ?") = 1 Then fMainForm.cmdAutorange.BackColor = &HFF00& Else fMainForm.cmdAutorange.BackColor = &H8000000F End If

End Sub

Public fMainForm As frmMain Public MGPIB As Integer Global RecContinue As Boolean Global Channel As Integer Sub Main() frmSplash.Show frmSplash.Refresh Set fMainForm = New frmMain Load fMainForm Unload frmSplash

264 fMainForm.Show InitializeGPIB WriteToSR785 "OUTX 0" ResetSR785ToNoise fMainForm.UpdateDisp MGPIB = 10 End Sub

Sub Wait(Time_in_ms As Integer) st = Timer While Timer - st < Time_in_ms / 1000 DoEvents Wend End Sub Function ChangeUnit(number As Single) As String If Abs(number) < 1 Then number = number * 1000 unit = " m" End If If Abs(number) < 1 Then number = number * 1000 unit = " u" End If If Abs(number) < 1 Then number = number * 1000 unit = " n" End If If Abs(number) < 1 Then number = number * 1000 unit = " p" End If ChangeUnit = Format(number, "000.0000") & unit End Function

VERSION 5.00 Object = "F9043C88-F6F2-101A-A3C9-08002B2F49FB#1.2#0"; "comdlg32.ocx" Object = "831FDD16-0C5C-11D2-A9FC-0000F8754DA1#2.0#0"; "MSCOMCTL.OCX" Begin VB.MDIForm frmMain BackColor = &H8000000C& Caption = "Viraj2004 SR785 Data Collector Program " ClientHeight = 10575 ClientLeft = 165 ClientTop = 735 ClientWidth = 15240 Icon = "frmMain.frx":0000 LinkTopic = "MDIForm1" StartUpPosition = 3 'Windows Default WindowState = 2 'Maximized

265 Begin VB.Timer Timer1 Interval = 300 Left = 1560 Top = 3000 End Begin VB.Timer Timer2 Enabled = 0 'False Interval = 200 Left = 4440 Top = 3000 End Begin MSComctlLib.Toolbar Toolbar2 Align = 2 'Align Bottom Height = 630 Left = 0 TabIndex = 6 Top = 9675 Width = 15240 _ExtentX = 26882 _ExtentY = 1111 ButtonWidth = 609 ButtonHeight = 953 Appearance = 1 _Version = 393216 Begin VB.CheckBox chkResetWhenComp Caption = "Reset when complete" Height = 375 Left = 11880 TabIndex = 31 Top = 120 Width = 1335 End Begin VB.TextBox Text9 Appearance = 0 'Flat BackColor = &H8000000F& BorderStyle = 0 'None BeginProperty Font Name = "Times New Roman" Size = 14.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 405 Left = 9840 MousePointer = 1 'Arrow TabIndex = 30 Text = "# Avgs" Top = 120 Width = 855 End Begin VB.TextBox txtNoAvg Alignment = 1 'Right Justify BackColor = &H00000000& BeginProperty Font

266 Name = "Arial" Size = 14.25 Charset = 0 Weight = 700 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty ForeColor = &H00FFFF00& Height = 375 Left = 10680 TabIndex = 29 Text = "500" ToolTipText = "Enter No of Averages" Top = 120 Width = 1215 End Begin VB.TextBox txtNoOfAvg Alignment = 1 'Right Justify BackColor = &H00000000& BeginProperty Font Name = "Arial" Size = 14.25 Charset = 0 Weight = 700 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty ForeColor = &H000000FF& Height = 375 Left = 13920 Locked = -1 'True TabIndex = 27 Text = "Done " ToolTipText = "No of Avg. Currently completed" Top = 120 Width = 1215 End Begin VB.TextBox Text1 Appearance = 0 'Flat BackColor = &H8000000F& BorderStyle = 0 'None BeginProperty Font Name = "Times New Roman" Size = 14.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 405 Left = 13320 MousePointer = 1 'Arrow TabIndex = 26 Text = "Avg."

267 Top = 120 Width = 615 End Begin VB.TextBox txtCenterF Alignment = 1 'Right Justify BackColor = &H00000000& BeginProperty Font Name = "Arial" Size = 14.25 Charset = 0 Weight = 700 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty ForeColor = &H0000FF00& Height = 375 Left = 4560 TabIndex = 25 Text = "52000" ToolTipText = "Center Frequency" Top = 120 Width = 1215 End Begin VB.TextBox Text10 Alignment = 2 'Center BackColor = &H00000000& BeginProperty Font Name = "Arial" Size = 14.25 Charset = 0 Weight = 700 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty ForeColor = &H0000FF00& Height = 375 Left = 9000 MousePointer = 1 'Arrow TabIndex = 14 Text = "Hz" Top = 120 Width = 615 End Begin VB.TextBox txtEndF Alignment = 1 'Right Justify BackColor = &H00000000& BeginProperty Font Name = "Arial" Size = 14.25 Charset = 0 Weight = 700 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty

268 ForeColor = &H0000FF00& Height = 375 Left = 7800 TabIndex = 13 Text = "102400" ToolTipText = "End Frequency" Top = 120 Width = 1215 End Begin VB.TextBox Text8 Appearance = 0 'Flat BackColor = &H8000000F& BorderStyle = 0 'None BeginProperty Font Name = "Times New Roman" Size = 14.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 405 Left = 6600 MousePointer = 1 'Arrow TabIndex = 12 Text = "End Freq. " Top = 120 Width = 1215 End Begin VB.TextBox Text7 Alignment = 2 'Center BackColor = &H00000000& BeginProperty Font Name = "Arial" Size = 14.25 Charset = 0 Weight = 700 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty ForeColor = &H0000FF00& Height = 375 Left = 5760 MousePointer = 1 'Arrow TabIndex = 11 Text = "Hz" Top = 120 Width = 615 End Begin VB.TextBox Text5 Appearance = 0 'Flat BackColor = &H8000000F& BorderStyle = 0 'None BeginProperty Font Name = "Times New Roman"

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270 Begin VB.TextBox txtStartF Alignment = 1 'Right Justify BackColor = &H00000000& BeginProperty Font Name = "Arial" Size = 14.25 Charset = 0 Weight = 700 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty ForeColor = &H0000FF00& Height = 375 Left = 1200 TabIndex = 7 Text = "0" ToolTipText = "Starting Frequency" Top = 120 Width = 1215 End End Begin MSComctlLib.Toolbar Toolbar1 Align = 3 'Align Left Height = 9255 Left = 0 TabIndex = 4 Top = 420 Width = 1035 _ExtentX = 1826 _ExtentY = 16325 ButtonWidth = 609 ButtonHeight = 953 Appearance = 1 _Version = 393216 BorderStyle = 1 Begin VB.OptionButton optDual Caption = "Dual" Height = 540 Left = 105 Style = 1 'Graphical TabIndex = 36 Top = 3570 Width = 750 End Begin VB.OptionButton optSingle Caption = "Single" Height = 540 Left = 105 Style = 1 'Graphical TabIndex = 35 Top = 3045 Value = -1 'True Width = 750 End Begin VB.CommandButton cmdLiveShow Caption = "SR785"

271 Height = 810 Left = 0 Picture = "frmMain.frx":0442 Style = 1 'Graphical TabIndex = 34 ToolTipText = "To access SR785 front panal button" Top = 4560 Width = 975 End Begin VB.CommandButton cmdRecordWhenAvg Caption = "Record 1 when Avg. complete " Height = 690 Left = 0 TabIndex = 28 ToolTipText = "To record spectrum after one avaragin cycle is completed" Top = 720 Width = 975 End Begin VB.CommandButton cmdRecContinually Caption = "Record Continually" Height = 690 Left = 0 Style = 1 'Graphical TabIndex = 24 ToolTipText = "To record spectrum end of every avaraging cycle" Top = 1440 Width = 975 End Begin VB.CommandButton cmdRec1Curve Caption = "Record One Curve" Height = 690 Left = 0 TabIndex = 23 ToolTipText = "To record current spectrum " Top = 0 Width = 975 End Begin VB.CommandButton cmdSR785 Caption = "SR785" Height = 810 Left = 0 Picture = "frmMain.frx":0F17 Style = 1 'Graphical TabIndex = 5 ToolTipText = "To access SR785 front panal button" Top = 2160 Width = 975 End Begin VB.Frame Frame1 BackColor = &H00C00000& Height = 3735 Left = 0 TabIndex = 15 Top = 5400 Width = 975 Begin VB.CommandButton cmdReset

272 Caption = "Full RESET" BeginProperty Font Name = "MS Serif" Size = 8.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 450 Left = 120 TabIndex = 22 ToolTipText = "To Reset SR785 its original configaration and set to noise measurment" Top = 3120 Width = 735 End Begin VB.CommandButton cmdAutoScale Caption = "Auto Scale" BeginProperty Font Name = "MS Serif" Size = 8.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 450 Left = 120 TabIndex = 21 ToolTipText = "Auto Scale SR785 Display" Top = 720 Width = 735 End Begin VB.CommandButton cmdResetNoise Caption = "Reset to noise" BeginProperty Font Name = "MS Serif" Size = 8.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 450 Left = 120 TabIndex = 20 ToolTipText = "To Reset SR785 for Noise measurments" Top = 2640 Width = 735 End Begin VB.CommandButton cmdSpanDown Caption = "Span Down" BeginProperty Font

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277 ImageKey = "Multi" EndProperty BeginProperty Button6 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "IV" Object.ToolTipText = "Get IV Curve" ImageKey = "IV" EndProperty BeginProperty Button7 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Setting" Object.ToolTipText = "Change Advance Setting" ImageKey = "Setting" EndProperty BeginProperty Button8 66833FEA-8583-11D1-B16A-00C0F0283628} Style = 3 EndProperty BeginProperty Button9 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Print" Object.ToolTipText = "Print" ImageKey = "Print" EndProperty BeginProperty Button10 66833FEA-8583-11D1-B16A-00C0F0283628} Style = 3 EndProperty BeginProperty Button11 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Cut" Object.ToolTipText = "Cut" ImageKey = "Cut" EndProperty BeginProperty Button12 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Copy" Object.ToolTipText = "Copy" ImageKey = "Copy" EndProperty BeginProperty Button13 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Paste" Object.ToolTipText = "Paste" ImageKey = "Paste" EndProperty BeginProperty Button14 66833FEA-8583-11D1-B16A-00C0F0283628} Style = 3 EndProperty BeginProperty Button15 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Bold" Object.ToolTipText = "Bold" ImageKey = "Bold" EndProperty BeginProperty Button16 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Italic" Object.ToolTipText = "Italic" ImageKey = "Italic" EndProperty BeginProperty Button17 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Underline" Object.ToolTipText = "Underline" ImageKey = "Underline" EndProperty BeginProperty Button18 66833FEA-8583-11D1-B16A-00C0F0283628}

278 Style = 3 EndProperty BeginProperty Button19 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Align Left" Object.ToolTipText = "Align Left" ImageKey = "Align Left" Style = 2 EndProperty BeginProperty Button20 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Center" Object.ToolTipText = "Center" ImageKey = "Center" Style = 2 EndProperty BeginProperty Button21 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Align Right" Object.ToolTipText = "Align Right" ImageKey = "Align Right" Style = 2 EndProperty BeginProperty Button22 66833FEA-8583-11D1-B16A-00C0F0283628} Style = 3 EndProperty BeginProperty Button23 66833FEA-8583-11D1-B16A-00C0F0283628} Key = "Drawing" Object.ToolTipText = "Drawing" ImageKey = "Drawing" EndProperty EndProperty Begin VB.TextBox Text11 Appearance = 0 'Flat BackColor = &H8000000F& BorderStyle = 0 'None BeginProperty Font Name = "Times New Roman" Size = 14.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 405 Left = 11160 MousePointer = 1 'Arrow TabIndex = 33 Text = "Timer" Top = 0 Width = 735 End Begin VB.TextBox txtTimer Alignment = 2 'Center BackColor = &H00000000& BeginProperty DataFormat Type = 1 Format = "H:mm:ss" HaveTrueFalseNull= 0

279 FirstDayOfWeek = 0 FirstWeekOfYear = 0 LCID = 1033 SubFormatType = 4 EndProperty BeginProperty Font Name = "BankGothic Lt BT" Size = 14.25 Charset = 0 Weight = 700 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty ForeColor = &H0000FF00& Height = 375 Left = 11880 TabIndex = 32 Text = "00:00:00" ToolTipText = "To Change GPIB Address of the Source Meter " Top = 0 Width = 1935 End Begin VB.TextBox Text2 Appearance = 0 'Flat BackColor = &H8000000F& BorderStyle = 0 'None BeginProperty Font Name = "Times New Roman" Size = 14.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 405 Left = 6840 MousePointer = 1 'Arrow TabIndex = 3 Text = "GPIB Address" Top = 0 Width = 1575 End Begin VB.TextBox txtGPIB Alignment = 2 'Center BeginProperty Font Name = "Times New Roman" Size = 14.25 Charset = 0 Weight = 700 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 375 Left = 8520

280 TabIndex = 2 Text = "2" ToolTipText = "To Change GPIB Address of the Source Meter " Top = 0 Width = 735 End End Begin VB.Menu mnuFile Caption = "&File" Begin VB.Menu mnuFileNew Caption = "&New" Shortcut = ^N End Begin VB.Menu mnuFileOpen Caption = "&Open..." Shortcut = ^O End Begin VB.Menu mnuFileClose Caption = "&Close" End Begin VB.Menu mnuFileBar0 Caption = "-" End Begin VB.Menu mnuFileSave Caption = "&Save" End Begin VB.Menu mnuFileSaveAs Caption = "Save &As..." End Begin VB.Menu mnuFileSaveAll Caption = "Save A&ll" End Begin VB.Menu mnuFileBar1 Caption = "-" End Begin VB.Menu mnuFileProperties Caption = "Propert&ies" End Begin VB.Menu mnuFileBar2 Caption = "-" End Begin VB.Menu mnuFilePageSetup Caption = "Page Set&up..." End Begin VB.Menu mnuFilePrintPreview Caption = "Print Pre&view" End Begin VB.Menu mnuFilePrint Caption = "&Print..." End Begin VB.Menu mnuFileBar3 Caption = "-" End Begin VB.Menu mnuFileSend Caption = "Sen&d..." End Begin VB.Menu mnuFileBar4

281 Caption = "-" End Begin VB.Menu mnuFileMRU Caption = "" Index = 1 Visible = 0 'False End Begin VB.Menu mnuFileMRU Caption = "" Index = 2 Visible = 0 'False End Begin VB.Menu mnuFileMRU Caption = "" Index = 3 Visible = 0 'False End Begin VB.Menu mnuFileBar5 Caption = "-" Visible = 0 'False End Begin VB.Menu mnuFileExit Caption = "E&xit" End End Begin VB.Menu mnuEdit Caption = "&Edit" Begin VB.Menu mnuEditUndo Caption = "&Undo" End Begin VB.Menu mnuEditBar0 Caption = "-" End Begin VB.Menu mnuEditCut Caption = "Cu&t" Shortcut = ^X End Begin VB.Menu mnuEditCopy Caption = "&Copy" Shortcut = ^C End Begin VB.Menu mnuEditPaste Caption = "&Paste" Shortcut = ^V End Begin VB.Menu mnuEditPasteSpecial Caption = "Paste &Special..." End End Begin VB.Menu mnuView Caption = "&View" Begin VB.Menu mnuViewToolbar Caption = "&Toolbar" Checked = -1 'True End Begin VB.Menu mnuViewStatusBar Caption = "Status &Bar"

282 Checked = -1 'True End Begin VB.Menu mnuViewBar0 Caption = "-" End Begin VB.Menu mnuViewRefresh Caption = "&Refresh" End Begin VB.Menu mnuViewOptions Caption = "&Options..." End Begin VB.Menu mnuViewWebBrowser Caption = "&Web Browser" End End Begin VB.Menu mnuTools Caption = "&Tools" Begin VB.Menu Calibrate Caption = "&MRD500 Calibration Data" Begin VB.Menu OpenCalFile Caption = "Open MRD500 Calibration File" End Begin VB.Menu SaveCalFile Caption = "Save As MRD500 Calibration File" End End Begin VB.Menu mnuToolsOptions Caption = "&Settings..." End End Begin VB.Menu mnuWindow Caption = "&Window" WindowList = -1 'True Begin VB.Menu mnuWindowNewWindow Caption = "&New Window" End Begin VB.Menu mnuWindowBar0 Caption = "-" End Begin VB.Menu mnuWindowCascade Caption = "&Cascade" End Begin VB.Menu mnuWindowTileHorizontal Caption = "Tile &Horizontal" End Begin VB.Menu mnuWindowTileVertical Caption = "Tile &Vertical" End Begin VB.Menu mnuWindowArrangeIcons Caption = "&Arrange Icons" End End Begin VB.Menu mnuHelp Caption = "&Help" Begin VB.Menu mnuHelpContents Caption = "&Contents" End

283 Begin VB.Menu mnuHelpSearchForHelpOn Caption = "&Search For Help On..." End Begin VB.Menu mnuHelpBar0 Caption = "-" End Begin VB.Menu mnuHelpAbout Caption = "&About " End End End Attribute VB_Name = "frmMain" Attribute VB_GlobalNameSpace = False Attribute VB_Creatable = False Attribute VB_PredeclaredId = True Attribute VB_Exposed = False Private Bpress As Boolean Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Any) As Long Const EM_UNDO = &HC7 Private Declare Function OSWinHelp% Lib "user32" Alias "WinHelpA" (ByVal hwnd&, ByVal HelpFile$, ByVal wCommand%, dwData As Any) Private ReSetComp As Boolean

Private Sub chkResetWhenComp_Click() ReSetComp = chkResetWhenComp.value End Sub

Private Sub cmdAutorange_Click() WriteToSR785 "KEYP 38" If Channel = 2 Then WriteToSR785 "KEYP 46" End If If QueriesSR785("A1RG ?") = 1 Then cmdAutorange.BackColor = &HFF00& Else cmdAutorange.BackColor = &H8000000F End If End Sub

Private Sub cmdAutoScale_Click() WriteToSR785 "KEYP 37" WriteToSR785 "KEYP 45" End Sub

Private Sub cmdLiveShow_Click() frmLive.Visible = True End Sub

Private Sub cmdRec1Curve_Click() ActiveForm.PlotCurve End Sub

Private Sub cmdRecContinually_Click() If RecContinue = False Then RecContinue = True

284 cmdRecContinually.BackColor = &HFF& Timer2.Enabled = True Else RecContinue = False cmdRecContinually.BackColor = &H8000000F Timer2.Enabled = False Timer1.Enabled = True End If End Sub

Private Sub cmdRecordWhenAvg_Click() RecContinue = False WriteToSR785 "KEYP 17" Timer2.Enabled = True End Sub

Private Sub cmdReset_Click() nl = Chr(10) & Chr(13) cho = MsgBox("This will RESET SR785 to its original configaration" & nl & "and reset parameters as suitable for Noise measurments." & nl & "Do you want to continue ?", vbYesNo, "Change system setings") If cho = 6 Then Timer2.Enabled = False WriteToSR785 "*RST" 'To Reset SR785 Wait 20000 MsgBox "aa" ResetSR785ToNoise Timer1.Enabled = False End If End Sub

Private Sub cmdResetNoise_Click() ResetSR785ToNoise End Sub

Private Sub cmdReStart_Click() WriteToSR785 "KEYP 17" End Sub

Private Sub cmdSpanDown_Click() WriteToSR785 "KEYP 61" fMainForm.UpdateDisp End Sub

Private Sub cmdSpanUp_Click() WriteToSR785 "KEYP 53" fMainForm.UpdateDisp End Sub

Private Sub cmdSR785_Click() ' If frmSR785.Visible = False Then frmSR785.Visible = True ' Else ' frmSR785.Visible = False ' End If End Sub

285 Private Sub MDIForm_Load() Me.Left = GetSetting(App.Title, "Settings", "MainLeft", 1000) Me.Top = GetSetting(App.Title, "Settings", "MainTop", 1000) Me.Width = GetSetting(App.Title, "Settings", "MainWidth", 7500) Me.Height = GetSetting(App.Title, "Settings", "MainHeight", 6500) MGPIB = GetSetting(App.Title, "Settings", "GPIB", 2) Me.txtGPIB = MGPIB ReSetComp = False LoadNewDoc Channel = 0 ' for single channel End Sub

Private Sub LoadNewDoc() Static lDocumentCount As Long Dim frmD As frmDocument lDocumentCount = lDocumentCount + 1 Set frmD = New frmDocument frmD.Caption = "Noise Spectrum Book " & lDocumentCount frmD.Width = Me.Width - 1400 frmD.Height = Me.Height - 2200 frmD.Show End Sub

Private Sub MDIForm_Unload(Cancel As Integer) If Me.WindowState <> vbMinimized Then SaveSetting App.Title, "Settings", "MainLeft", Me.Left SaveSetting App.Title, "Settings", "MainTop", Me.Top SaveSetting App.Title, "Settings", "MainWidth", Me.Width SaveSetting App.Title, "Settings", "MainHeight", Me.Height SaveSetting App.Title, "Settings", "GPIB", MGPIB End If ilonl Dev%, 0 Close All End End Sub

Private Sub optDual_Click() If optDual.value = True Then Channel = 2 ' for both channel frmDualRecord.Visible = True DoEvents ResetSR785ToNoise End If End Sub

Private Sub optSingle_Click() If optSingle.value = True Then Channel = 0 DoEvents ResetSR785ToNoise End If End Sub

Private Sub tbToolBar_ButtonClick(ByVal Button As MSComctlLib.Button) On Error Resume Next Select Case Button.Key Case "New"

286 LoadNewDoc Case "Open" mnuFileOpen_Click Case "Save" mnuFileSave_Click Case "Multi" Static v If v = 0 Then v = 1 Else v = 0 frmSR785.Visible = v Button.value = v Case "IV"

Case "Setting"

Private Sub mnuHelpAbout_Click() frmAbout.Show vbModal, Me End Sub

Private Sub mnuHelpSearchForHelpOn_Click() Dim nRet As Integer

'if there is no helpfile for this project display a message to the user 'you can set the HelpFile for your application in the 'Project Properties dialog

287 If Len(App.HelpFile) = 0 Then MsgBox "Unable to display Help Contents. There is no Help associated with this project.", vbInformation, Me.Caption Else On Error Resume Next nRet = OSWinHelp(Me.hwnd, App.HelpFile, 261, 0) If Err Then MsgBox Err.Description End If End If

End Sub

Private Sub mnuHelpContents_Click() Dim nRet As Integer

'if there is no helpfile for this project display a message to the user 'you can set the HelpFile for your application in the 'Project Properties dialog If Len(App.HelpFile) = 0 Then MsgBox "Unable to display Help Contents. There is no Help associated with this project.", vbInformation, Me.Caption Else On Error Resume Next nRet = OSWinHelp(Me.hwnd, App.HelpFile, 3, 0) If Err Then MsgBox Err.Description End If End If

End Sub

Private Sub mnuWindowArrangeIcons_Click() Me.Arrange vbArrangeIcons End Sub

Private Sub mnuWindowTileVertical_Click() Me.Arrange vbTileVertical End Sub

Private Sub mnuWindowTileHorizontal_Click() Me.Arrange vbTileHorizontal End Sub

Private Sub mnuWindowCascade_Click() Me.Arrange vbCascade End Sub

Private Sub mnuWindowNewWindow_Click() LoadNewDoc End Sub

Private Sub mnuToolsOptions_Click() frmOptions.Show vbModal, Me End Sub

288

Private Sub mnuViewOptions_Click() frmOptions.Show vbModal, Me End Sub

Private Sub mnuViewRefresh_Click() 'ToDo: Add 'mnuViewRefresh_Click' code. MsgBox "Add 'mnuViewRefresh_Click' code." End Sub

Private Sub mnuViewStatusBar_Click() mnuViewStatusBar.Checked = Not mnuViewStatusBar.Checked sbStatusBar.Visible = mnuViewStatusBar.Checked End Sub

Private Sub mnuViewToolbar_Click() mnuViewToolbar.Checked = Not mnuViewToolbar.Checked tbToolBar.Visible = mnuViewToolbar.Checked End Sub

Private Sub mnuEditPasteSpecial_Click() 'ToDo: Add 'mnuEditPasteSpecial_Click' code. MsgBox "Add 'mnuEditPasteSpecial_Click' code." End Sub

Private Sub mnuEditPaste_Click() On Error Resume Next ' ActiveForm.rtfText.SelRTF = Clipboard.GetText

End Sub

Private Sub mnuEditCopy_Click() On Error Resume Next ' Clipboard.SetText ActiveForm.rtfText.SelRTF

End Sub

Private Sub mnuEditCut_Click() On Error Resume Next ' Clipboard.SetText ActiveForm.rtfText.SelRTF ' ActiveForm.rtfText.SelText = vbNullString

End Sub

Private Sub mnuEditUndo_Click() 'ToDo: Add 'mnuEditUndo_Click' code. MsgBox "Add 'mnuEditUndo_Click' code." End Sub

Private Sub mnuFileExit_Click() ilonl Dev%, 0 Close All End End Sub

Private Sub mnuFileSend_Click()

289 'ToDo: Add 'mnuFileSend_Click' code. MsgBox "Add 'mnuFileSend_Click' code." End Sub

Private Sub mnuFilePrint_Click() On Error Resume Next If ActiveForm Is Nothing Then Exit Sub

End Sub

Private Sub mnuFilePrintPreview_Click() 'ToDo: Add 'mnuFilePrintPreview_Click' code. MsgBox "Add 'mnuFilePrintPreview_Click' code." End Sub

Private Sub mnuFilePageSetup_Click() On Error Resume Next With dlgCommonDialog .DialogTitle = "Page Setup" .CancelError = True .ShowPrinter End With

End Sub

Private Sub mnuFileProperties_Click() 'ToDo: Add 'mnuFileProperties_Click' code. MsgBox "Add 'mnuFileProperties_Click' code." End Sub

Private Sub mnuFileSaveAll_Click() 'ToDo: Add 'mnuFileSaveAll_Click' code. MsgBox "Add 'mnuFileSaveAll_Click' code." End Sub

Private Sub mnuFileSaveAs_Click() If ActiveForm.Caption <> "Viraj2003 Multimeter" Then ActiveForm.SaveAs Else frmSR785.WindowState = 1 ActiveForm.SaveAs frmSR785.WindowState = 0

290 End If End Sub

Private Sub mnuFileSave_Click() If ActiveForm.Caption <> "Viraj2003 Multimeter" Then ActiveForm.Save Else frmSR785.WindowState = 1 ActiveForm.Save frmSR785.WindowState = 0 End If End Sub

Private Sub mnuFileClose_Click() 'ToDo: Add 'mnuFileClose_Click' code. MsgBox "Add 'mnuFileClose_Click' code." End Sub

Private Sub mnuFileOpen_Click() LoadNewDoc ActiveForm.Fopen End Sub

Private Sub mnuFileNew_Click() LoadNewDoc End Sub

Public Sub multioff() tbToolBar.Buttons.Item(5).value = tbrUnpressed End Sub

Private Sub Timer1_Timer() nAvg = QueriesSR785("NAVG ? 0") If nAvg > Val(txtNoAvg) And ReSetComp = True Then WriteToSR785 "KEYP 17" End If txtNoOfAvg.Text = nAvg DoEvents End Sub

Private Sub Timer2_Timer() nAvg = QueriesSR785("NAVG ? 0")

If nAvg < Val(txtNoAvg) Then txtNoOfAvg.Text = nAvg DoEvents Else Timer2.Enabled = False DoEvents ActiveForm.PlotCurve End If End Sub

Private Sub txtCenterF_Validate(Cancel As Boolean) If txtStartF >= 0 Then a$ = "FCTR 0, " & txtCenterF WriteToSR785 a$

291 UpdateDisp End If End Sub

Private Sub txtEndF_Validate(Cancel As Boolean) If txtStartF >= 0 Then a$ = "FSPN 0, " & txtEndF WriteToSR785 a$ UpdateDisp End If

End Sub

Private Sub txtGPIB_Change() MGPIB = txtGPIB.Text End Sub

Private Sub txtStart_Change() ActiveForm.SetScale txtStart, txtStop End Sub

Private Sub txtStop_Change() ActiveForm.SetScale txtStart, txtStop End Sub Sub UpdateDisp() txtStartF.Text = Format(QueriesSR785("FSTR ? 0"), "#0.0##") txtCenterF.Text = Format(QueriesSR785("FCTR ? 0"), "#####") txtEndF.Text = Format(QueriesSR785("FSPN ? 0"), "######") End Sub

Private Sub txtNoAvg_Change() a$ = "FAVN 0," & txtNoAvg WriteToSR785 a$ End Sub

Private Sub txtStartF_Validate(Cancel As Boolean) If txtStartF >= 0 Then a$ = "FSTR 0, " & txtStartF WriteToSR785 a$ UpdateDisp End If End Sub

292 Dim oBook As Excel.Workbook Dim oSheet As Excel.Worksheet Dim oChart As Excel.Chart Dim NoG As Long Dim data(1 To 1000, 1 To 2) As Single

Private Sub cmbDescription_Click() txtCellNo = cmbDescription.ListIndex + 1 DescripChange End Sub

Private Sub cmbDescription_DropDown() DescripChange End Sub

Private Sub cmbDescription_KeyPress(KeyAscii As Integer) If KeyAscii = 13 Then DescripChange End If End Sub

Private Sub cmbDescription_LostFocus() DescripChange End Sub Sub DescripChange() cmbDescription.List(txtCellNo - 1) = cmbDescription.Text cmbDescription.ListIndex = txtCellNo - 1 If NoG > 0 Then oSheet.Cells(3, (2 * txtCellNo)).value = cmbDescription.List(txtCellNo - 1) End If End Sub

Private Sub Form_Load() cmbDescription.List(0) = "Noise Curve " cmbDescription.ListIndex = 0 txtCellNo = cmbDescription.ListIndex + 1

OLE1.CreateEmbed "", "excel.chart" Set oBook = OLE1.object Set oChart = oBook.Charts(1) Set oSheet = oBook.Worksheets(1)

oSheet.Cells.Clear oChart.ChartType = xlXYScatterSmoothNoMarkers oChart.SetSourceData oSheet.Range("A3:B804"), xlColumns With oChart

.HasTitle = True .ChartTitle.AutoScaleFont = False .ChartTitle.Font.Size = 12 .ChartTitle.Text = "Noise Spectrum of the Sample" .HasLegend = True .Legend.Interior.ColorIndex = xlNone .Legend.Border.LineStyle = xlNone .Legend.AutoScaleFont = False .Legend.Font.Size = 8

293 .Legend.Left = 200 .Legend.Top = 60 .Axes(xlCategory, xlPrimary).HasTitle = True .Axes(xlCategory, xlPrimary).AxisTitle.AutoScaleFont = False .Axes(xlCategory, xlPrimary).AxisTitle.Font.Size = 12 .Axes(xlCategory, xlPrimary).AxisTitle.Characters.Text = "Frequency (Hz)" .Axes(xlValue, xlPrimary).HasTitle = True .Axes(xlValue, xlPrimary).AxisTitle.Characters.Text = "Noise Voltage Density (Vrms²/Hz)" .Axes(xlValue, xlPrimary).AxisTitle.AutoScaleFont = False .Axes(xlValue, xlPrimary).AxisTitle.Font.Size = 12 End With With oChart.Axes(xlValue) .HasMajorGridlines = False .HasMinorGridlines = False .MajorTickMark = xlInside .MinorTickMark = xlInside .TickLabelPosition = xlNextToAxis .TickLabels.AutoScaleFont = False ' .TickLabels.NumberFormat = "0.00" .TickLabels.Font.Size = 12 '.MinimumScale = 1 '.MaximumScale = 1 ' .Crosses = xlCustom ' .CrossesAt = .MinimumScale .ScaleType = xlLogarithmic End With With oChart.Axes(xlCategory) .HasMajorGridlines = False .HasMinorGridlines = False .MajorTickMark = xlInside .MinorTickMark = xlInside .TickLabelPosition = xlNextToAxis .TickLabels.AutoScaleFont = False ' .TickLabels.NumberFormat = "0.00" .TickLabels.Font.Size = 12 '.MinimumScale = 400 '.MaximumScale = 1200 .ScaleType = xlLogarithmic End With

oChart.PlotArea.Interior.ColorIndex = xlNone

OLE1.Visible = True ' OLE1.Close 'Deactivate the OLE container Application.Assistant.Visible = True With oSheet .Cells(1, 1).value = "Viraj2004 Noise Spectrum Recorder Data File" .Cells(2, 1).value = "Vrms²/Hz vs Freq." End With End Sub Private Sub Form_Resize() On Error Resume Next OLE1.Move 100, 480, Me.ScaleWidth - 200, Me.ScaleHeight - 1100 sldpos.Left = 120 sldpos.Top = Me.ScaleHeight - 500

294 sldpos.Width = Me.ScaleWidth - 240

End Sub Sub Fopen() Dim sFile As String With CommonDialog .DialogTitle = "Open" .CancelError = False .Filter = "Excel File (*.xls)|*.xls" .DialogTitle = "Open Noise Spectrum File" .ShowOpen If Len(.filename) = 0 Then Exit Sub End If sFile = .filename End With Caption = sFile

OLE1.CreateEmbed sFile, "excel.chart" Set oBook = OLE1.object Set oSheet = oBook.Worksheets(1)

With oSheet If Left(.Cells(1, 1).value, 43) <> "Viraj2004 Noise Spectrum Recorder Data File" Then MsgBox "This is not a Viraj 2003 Action spectrum Data file", vbOKOnly + vbInformation, "Invalied file format" Exit Sub End If Set oChart = oBook.Charts(1) c = 1 xx = .Cells(1, c).value While xx <> "" c = c + 2 xx = .Cells(1, c).value Wend End With NoG = (c - 1) / 2 For z% = 1 To NoG cmbDescription.List(z% - 1) = oSheet.Cells(3, 2 * z%).value Next z% cmbDescription.AddItem "Sample No " & LTrim(Str(NoG + 1)) End Sub

Sub Save() Dim sFile As String If Left$(Caption, 19) = "Noise Spectrum Book" Then On Error GoTo ErrHandler With CommonDialog .CancelError = True .Filter = "Excel File (*.xls)|*.xls" .DialogTitle = "Save Noise Spectrum Data File" .Flags = cdlOFNOverwritePrompt .ShowSave If Len(.filename) = 0 Then Exit Sub End If

295 sFile = .filename End With oBook.SaveCopyAs sFile Caption = sFile Else sFile = Caption oBook.SaveCopyAs sFile End If ErrHandler: Exit Sub End Sub

Sub SaveAs() Dim sFile As String On Error GoTo ErrHandler With CommonDialog .CancelError = True .Filter = "Excel File (*.xls)|*.xls" .DialogTitle = "Save Noise Spectrum Data File As" .Flags = cdlOFNOverwritePrompt .ShowSave If Len(.filename) = 0 Then Exit Sub End If sFile = .filename End With oBook.SaveCopyAs sFile Caption = sFile

ErrHandler: Exit Sub End Sub

Sub PlotCurve() 'Dim data(1 To 810, 1 To 2) As Single fMainForm.Timer1.Enabled = False fMainForm.Timer2.Enabled = False fMainForm.tbToolBar.Enabled = False MousePointer = 11 WriteToSR785 "KEYP 25"

NoG = NoG + 1 Cn% = (NoG * 2) - 1 Rn% = 4

With oSheet .Cells(3, Cn%).value = "f (Hz)" If NoG > 1 Then If (Right(cmbDescription.List(NoG - 2), 2) = "AM" Or Right(cmbDescription.List(NoG - 2), 2) = "PM") And Len(cmbDescription.List(NoG - 2)) > 12 Then cmbDescription.List(NoG - 1) = Left(cmbDescription.List(NoG - 2), Len(cmbDescription.List(NoG - 2)) - 11) & " " & Time Else cmbDescription.List(NoG - 1) = "Noise Curve " & Trim(Str(NoG)) & " " & Time End If

296 Else cmbDescription.List(NoG - 1) = cmbDescription.List(0) & " " & Time End If .Cells(3, Cn% + 1).value = cmbDescription.List(NoG - 1)

cmbDescription.ListIndex = NoG - 1 txtCellNo = cmbDescription.ListIndex + 1 DoEvents n = QueriesSR785("DSPN ? 0") - 1 StartF = QueriesSR785("FSPN ? 0") / n

fMainForm.txtNoOfAvg.Text = "Reading..." fMainForm.sbStatusBar.Panels(1).Text = "Data Collecting in Progress..." WriteToSR785 "TONE 50,55" DoEvents

WriteToSR785 "DSPY ? 0" a$ = ReadSR785()

WriteToSR785 "TONE 50,55"

fMainForm.sbStatusBar.Panels(1).Text = "Data Plotting..."

WriteToSR785 "KEYP 17" fMainForm.Timer1.Enabled = True

.Cells(Rn%, Cn%).value = StartF .Cells(Rn%, Cn% + 1).value = Val(Mid(a$, 17, 15)) Rn% = Rn% + 1 If NoG > 1 Then oChart.SeriesCollection.NewSeries oChart.SeriesCollection(NoG).XValues = .Range(.Cells(4, Cn%), .Cells(804, Cn%)) oChart.SeriesCollection(NoG).Values = .Range(.Cells(4, Cn% + 1), .Cells(804, Cn% + 1)) End If oChart.SeriesCollection(NoG).Name = .Range(.Cells(3, Cn% + 1), .Cells(3, Cn% + 1)) '####################################################################### For i = 2 To n 'data(i, 1) = i * StartF ' data(i, 2) = Val(Mid(a$, (16 * i) + 1, 15))

.Cells(Rn%, Cn%).value = i * StartF .Cells(Rn%, Cn% + 1).value = Val(Mid(a$, (16 * i) + 1, 15)) Rn% = Rn% + 1 DoEvents Next i '.Range(Cells(Rn%, Cn%), Cells(Rn% + n, Cn% + 1)).value = data() '.Range(Cells(2, Cn%), Cells(2 + n, Cn% + 1)).value = data()

'#######################################################################

End With oChart.Axes(xlValue).Crosses = xlCustom oChart.Axes(xlValue).CrossesAt = oChart.Axes(xlValue).MinimumScale

297 fMainForm.sbStatusBar.Panels(1).Text = "Done"

If RecContinue = True Then fMainForm.Timer1.Enabled = False fMainForm.Timer2.Enabled = True Else fMainForm.Timer1.Enabled = True End If

fMainForm.tbToolBar.Enabled = True MousePointer = 0 End Sub Private Sub txtArea_Change() If txtArea = "" Then txtArea = 0 If txtArea > 0 Then With oSheet Voc = .Cells(4, txtCellNo * 2).value Isc = .Cells(5, txtCellNo * 2).value FF = .Cells(6, txtCellNo * 2).value Eff = .Cells(7, txtCellNo * 2).value area = .Cells(10, txtCellNo * 2).value Eff = Eff * area / txtArea .Cells(7, txtCellNo * 2).value = Format(Eff, "#0.000") .Cells(10, txtCellNo * 2).value = Val(txtArea) End With End If End Sub

Private Sub txtCellNo_Click() CommonDialog.ShowColor If NoG > 0 Then With oChart.SeriesCollection(Val(txtCellNo)) .Border.Color = CommonDialog.Color End With End If End Sub

Private Sub txtIntencity_Change() If txtIntencity = "" Then txtIntencity = 0 If txtIntencity > 0 Then With oSheet Voc = .Cells(4, txtCellNo * 2).value Isc = .Cells(5, txtCellNo * 2).value FF = .Cells(6, txtCellNo * 2).value Eff = .Cells(7, txtCellNo * 2).value Inten = .Cells(11, txtCellNo * 2).value Eff = Eff * Inten / txtIntencity .Cells(7, txtCellNo * 2).value = Format(Eff, "#0.000") .Cells(11, txtCellNo * 2).value = Val(txtIntencity) End With End If End Sub

Sub SetScale(Min As Single, Max As Single) oChart.Axes(xlCategory).MinimumScale = Min oChart.Axes(xlCategory).MaximumScale = Max End Sub

298

*********************************************************************** frmSR785.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private Sub cmdAutorange_Click() WriteToSR785 "KEYP 38" If QueriesSR785("A1RG ?") = 1 Then lblAutoRange.Visible = True Else lblAutoRange.Visible = False End If End Sub

Private Sub cmdAutoScale_Click() WriteToSR785 "KEYP 37" End Sub

Private Sub cmdAvg_Click() i = QueriesSR785("FLIN ? 0") If i = 3 Then i = 0 Else i = i + 1 End If a$ = "FLIN 0, " & i WriteToSR785 a$ lblFFTLines.Caption = Trim(Str(100 * 2 ^ i)) End Sub

Private Sub cmdPauseCont_Click() WriteToSR785 "KEYP 25" End Sub

Private Sub cmdSpanDwn_Click() WriteToSR785 "KEYP 61" lblStartF.Caption = Format(QueriesSR785("FSTR ? 0"), "#0.0## Hz") lblEndF.Caption = Format(QueriesSR785("FSPN ? 0"), "##### Hz") fMainForm.UpdateDisp End Sub

Private Sub cmdSpanUp_Click() WriteToSR785 "KEYP 53" lblStartF.Caption = Format(QueriesSR785("FSTR ? 0"), "#0.0## Hz") lblEndF.Caption = Format(QueriesSR785("FSPN ? 0"), "##### Hz") fMainForm.UpdateDisp End Sub

Private Sub cmdStart_Click() WriteToSR785 "KEYP 17" End Sub

299 Private Sub Form_Load() If QueriesSR785("A1RG ?") = 1 Then lblAutoRange.Visible = True Else lblAutoRange.Visible = False End If lblStartF.Caption = Format(QueriesSR785("FSTR ? 0"), "#0.0## Hz") lblEndF.Caption = Format(QueriesSR785("FSPN ? 0"), "##### Hz") lblFFTLines.Caption = 100 * 2 ^ QueriesSR785("FLIN ? 0") End Sub

*********************************************************************** frmDualRecord.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Private Sub cmdBrows_Click() On Error Resume Next With CommonDialog1 .DialogTitle = "Enter File Name to store data" .CancelError = True .Filter = "All File (*.*)|*.*" .Flags = cdlOFNOverwritePrompt .ShowSave txtFileName.Text = .filename End With End Sub

Private Sub cmdExit_Click() Close All frmDualRecord.Visible = False End Sub

Private Sub cmdStart_Click() Timer1.Enabled = True Timer1_Timer End Sub

Private Sub cmdStop_Click() Timer1.Enabled = False End Sub

Private Sub Form_Load() Me.Height = 4260 Me.Width = 5460

End Sub

Private Sub Timer1_Timer() Static cc As Long cc = cc + 1 lblNoofCurves.Caption = Trim(Str(cc)) MousePointer = 11 WriteToSR785 "KEYP 25" tt$ = Str(Hour(Time)) + "-" + Str(Minute(Time)) + "-" + Str(Second(Time))

300 fName = txtFileName.Text + "-" + tt$ + ".txt" Open fName For Output As #1 Print #1, "f(Hz)", "A" & tt$, "B" & tt$

n = QueriesSR785("DSPN ? 0") - 1 StartF = QueriesSR785("FSPN ? 0") / n WriteToSR785 "TONE 50,55" WriteToSR785 "DSPY ? 0" a$ = ReadSR785() WriteToSR785 "DSPY ? 1" b$ = ReadSR785() WriteToSR785 "TONE 50,55" WriteToSR785 "KEYP 17"

For i = 1 To n Print #1, i * StartF, Mid(a$, (16 * i) + 1, 15), Mid(b$, (16 * i) + 1, 15) Next i

MousePointer = 0 Close #1

End Sub

Private Sub txtTime_Change() Timer1.Interval = Val(txtTime.Text) * 60000 End Sub

301 B.4 x-z-θ stage controller

An inexpensive x-z-θ sample stage was constructed and tested. This stage can be used with an FT-

IR to perform transmission measurements at different points on the samples at different incident angles with 80 µm special resolution in the x-z directions and 1-degree accuracy in the angle θ.

The mechanical part of the stage was constructed by using stepper motors removed from old computer floppy disk drives. A software program was developed to control this stage using Visual

Basic. The user interface is shown in Figure B.25.

302

Figure B.24 Photgraphs of the x-z-θ stage (top) showing moving directions and placement in the FTIR sample compartment and (bottom) a closer view of the mechanical parts.

303

B.4.1 User interface

304 B.4.2 Source code

*********************************************************************** x-y Stage.frm *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Begin VB.Form Form1 Caption = "Viraj2006 2D Stage controller" ClientHeight = 5520 ClientLeft = 60 ClientTop = 345 ClientWidth = 3960 LinkTopic = "Form1" MaxButton = 0 'False ScaleHeight = 5520 ScaleWidth = 3960 StartUpPosition = 3 'Windows Default Begin VB.Frame Frame1 Height = 2640 Left = 0 TabIndex = 5 Top = 0 Width = 1800 Begin VB.CommandButton cmdGo Caption = "Go" Height = 645 Left = 1155 TabIndex = 11 Top = 1890 Width = 540 End Begin VB.Frame Frame4 Height = 1600 Left = 100 TabIndex = 8 Top = 200 Width = 1600 Begin VB.Shape Shape1 BackColor = &H000000FF& BackStyle = 1 'Opaque BorderColor = &H000000FF& Height = 100 Left = 750 Shape = 3 'Circle Top = 750 Width = 100 End Begin VB.Shape Shape2 BorderColor = &H0000FF00& Height = 400 Left = 600 Shape = 3 'Circle Top = 600 Width = 400

305 End Begin VB.Line Line2 BorderColor = &H0000FF00& X1 = 500 X2 = 1100 Y1 = 800 Y2 = 800 End Begin VB.Line Line3 BorderColor = &H0000FF00& X1 = 795 X2 = 795 Y1 = 500 Y2 = 1100 End Begin VB.Shape shpSample BackColor = &H00000040& BackStyle = 1 'Opaque BorderColor = &H80000005& FillColor = &H00808080& FillStyle = 0 'Solid Height = 800 Left = 800 Top = 0 Width = 800 End Begin VB.Shape Shape3 BackColor = &H00000040& BackStyle = 1 'Opaque Height = 1605 Left = 0 Top = 0 Width = 1605 End End Begin VB.TextBox txtX BackColor = &H00000000& ForeColor = &H0000FF00& Height = 330 Left = 420 TabIndex = 7 Text = "0" Top = 1890 Width = 645 End Begin VB.TextBox txtZ BackColor = &H00000000& ForeColor = &H0000FF00& Height = 330 Left = 420 TabIndex = 6 Text = "0" Top = 2205 Width = 645 End Begin VB.Label Label1 Caption = "x ="

306 BeginProperty Font Name = "MS Sans Serif" Size = 9.75 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 330 Left = 105 TabIndex = 10 Top = 1890 Width = 330 End Begin VB.Label Label2 Caption = "z =" BeginProperty Font Name = "MS Sans Serif" Size = 9.75 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 330 Left = 105 TabIndex = 9 Top = 2205 Width = 330 End End Begin VB.Frame Frame3 Height = 2640 Left = 1890 TabIndex = 4 Top = 0 Width = 2010 Begin VB.Timer Timer2 Enabled = 0 'False Interval = 60 Left = 1470 Top = 1470 End Begin VB.CommandButton cmdDirection Height = 500 Index = 3 Left = 210 Picture = "x-y Stage.frx":0000 Style = 1 'Graphical TabIndex = 20 Top = 735 Width = 500 End Begin VB.CommandButton cmdDirection Height = 500

307 Index = 2 Left = 735 Picture = "x-y Stage.frx":007E Style = 1 'Graphical TabIndex = 19 Top = 1260 Width = 500 End Begin VB.CommandButton cmdDirection Height = 500 Index = 1 Left = 1260 Picture = "x-y Stage.frx":00F7 Style = 1 'Graphical TabIndex = 18 Top = 735 Width = 500 End Begin VB.CommandButton cmdInitialize Caption = "Initialize" Height = 330 Left = 210 TabIndex = 12 Top = 1890 Width = 1485 End Begin VB.CheckBox chkKeyBoard Caption = "Enable keyboard" Height = 255 Left = 210 TabIndex = 2 Top = 2310 Width = 1650 End Begin VB.Timer Timer1 Enabled = 0 'False Interval = 50 Left = 105 Top = 210 End Begin VB.CommandButton cmdDirection Height = 500 Index = 0 Left = 735 Picture = "x-y Stage.frx":0175 Style = 1 'Graphical TabIndex = 0 Top = 210 Width = 500 End Begin VB.CommandButton cmdSave Caption = "Save" Height = 500 Left = 735 Style = 1 'Graphical TabIndex = 1 ToolTipText = "Click to Save Current Location"

308 Top = 735 Width = 500 End End Begin VB.Frame Frame2 Caption = "Saved Lacations" Height = 2745 Left = 0 TabIndex = 3 Top = 2730 Width = 3900 Begin VB.CommandButton cmdCompact Caption = "Compact Mode" BeginProperty Font Name = "Arial Narrow" Size = 8.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = 0 'False Strikethrough = 0 'False EndProperty Height = 330 Left = 2730 TabIndex = 16 Top = 210 Width = 1065 End Begin VB.PictureBox pic1 BackColor = &H00000080& ForeColor = &H0000FF00& Height = 2400 Left = 105 ScaleHeight = 80 ScaleMode = 0 'User ScaleWidth = 80 TabIndex = 14 Top = 210 Width = 2400 Begin VB.Label lblPos Appearance = 0 'Flat BackColor = &H0000FFFF& ForeColor = &H80000008& Height = 60 Index = 0 Left = 0 MouseIcon = "x-y Stage.frx":01C0 MousePointer = 99 'Custom TabIndex = 17 Top = 2340 Width = 60 End End Begin VB.Label Label4 Caption = "Click [Shift] + [Right mouse button] to Delete Location" Height = 855

309 Left = 2625 TabIndex = 15 Top = 1680 Width = 1170 End Begin VB.Label Label3 Caption = "Click a Location to move the sample" Height = 750 Left = 2625 TabIndex = 13 Top = 735 Width = 1170 End End End Attribute VB_Name = "Form1" Attribute VB_GlobalNameSpace = False Attribute VB_Creatable = False Attribute VB_PredeclaredId = True Attribute VB_Exposed = False Public BPress As Boolean Dim CPx As Integer Dim CPz As Integer Dim n As Integer Dim DKey As Integer Dim Location(1 To 100, 1 To 2) As Integer

Private Sub chkKeyBoard_Click() If chkKeyBoard.Value = 1 Then Timer1.Enabled = True Else Timer1.Enabled = False End If End Sub

Private Sub cmdCompact_Click() Form1.Height = 3090 End Sub

Private Sub cmdDirection_MouseDown(Index As Integer, Button As Integer, Shift As Integer, X As Single, Y As Single) DKey = Index Timer2.Enabled = True End Sub

Private Sub cmdDirection_MouseUp(Index As Integer, Button As Integer, Shift As Integer, X As Single, Y As Single) Timer2.Enabled = False End Sub

Private Sub cmdGo_Click() GoPos Int(txtX.Text), Int(txtZ.Text) End Sub

Private Sub cmdInitialize_Click() Initialize End Sub

310

Private Sub lblPos_Click(Index As Integer) NewX% = Location(Index, 1) NewZ% = Location(Index, 2) GoPos NewX%, NewZ% End Sub

Private Sub lblpos_MouseDown(Index As Integer, Button As Integer, Shift As Integer, X As Single, Y As Single) If Button = 2 And Shift = 1 Then Unload lblPos(Index) Location(Index, 1) = -1 Location(Index, 2) = -1

End If End Sub

Private Sub cmdSave_Click() For i = 1 To n If Location(i, 1) = CPx And Location(i, 2) = CPz Then MsgBox "You already Saved This Location", vbExclamation Exit Sub End If Next i n = n + 1 Form1.Height = 5925 Load lblPos(n) lblPos(n).Top = 80 - CPz lblPos(n).Left = CPx lblPos(n).Visible = True Location(n, 1) = CPx Location(n, 2) = CPz lblPos(n).ToolTipText = "Location " & n & " (" & CPx & "," & CPz & ")" End Sub

Private Sub cmdUp_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) BPress = True While BPress = True shpSample.Top = shpSample.Top - 10 DoEvents n = 1 While n < 25000 n = n + 1 Wend Wend

End Sub

Private Sub cmdUp_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single) BPress = False End Sub Private Sub cmdDown_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)

311 BPress = True While BPress = True shpSample.Top = shpSample.Top + 10 DoEvents n = 1 While n < 25000 n = n + 1 Wend Wend

End Sub

Private Sub cmdDown_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single) BPress = False

End Sub

Private Sub Command2_Click() For ii = 1 To 10 For i = 1 To 70 Out &H378, 2 Out &H378, 3 Wait 5 DoEvents Next i For i = 1 To 70 Out &H378, 0 Out &H378, 1 Wait 5 DoEvents Next i Next ii End Sub

Private Sub Form_Load() ' Form1.Height = 3090 Form1.Show n = 0 Initialize End Sub

Private Sub pic1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) If Button = 1 Then GoPos CInt(X), CInt(80 - Y) End If End Sub

Private Sub pic1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single) pic1.ToolTipText = CInt(X) & "," & CInt(80 - Y)

End Sub

Private Sub Timer1_Timer()

312 If GetKeyState(vbKeyDown) And CPz < 80 And KeyDown Then Out &H378, 10 Out &H378, 11 Form1.shpSample.Top = Form1.shpSample.Top + 10 CPz = CPz + 1 txtZ.Text = CPz End If If GetKeyState(vbKeyUp) And CPz > 0 And KeyDown Then Out &H378, 8 Out &H378, 9 Form1.shpSample.Top = Form1.shpSample.Top - 10 CPz = CPz - 1 txtZ.Text = CPz End If If GetKeyState(vbKeyLeft) And CPx < 80 And KeyDown Then Out &H378, 6 Out &H378, 7 Form1.shpSample.Left = Form1.shpSample.Left - 10 CPx = CPx + 1 txtX.Text = CPx End If If GetKeyState(vbKeyRight) And CPx > 0 And KeyDown Then Out &H378, 4 Out &H378, 5 Form1.shpSample.Left = Form1.shpSample.Left + 10 CPx = CPx - 1 txtX.Text = CPx End If End Sub Sub Initialize() ' ********************************* ' To find z motor track zero ' ********************************* Out &H378, 10 If Inp(&H379) = 56 Then For i = 1 To 15 Out &H378, 8 Out &H378, 9 Wait 5 DoEvents Next i End If i = 1 While i < 90 And Inp(&H379) = 120 Out &H378, 10 Out &H378, 11 Wait 5 DoEvents i = i + 1 Wend If i = 90 Then MsgBox "Initialization failed. Please check all the cables and power supply and press [Initialize] button.", vbCritical, "Error... Initialization Failed" Exit Sub Else For i = 1 To 80

313 Out &H378, 8 Out &H378, 9 Wait 5 DoEvents Next i

Form1.shpSample.Top = 0 CPz = 0 txtX.Text = 0 End If

' ********************************* ' To find x motor track zero ' ********************************* Out &H378, 6 If Inp(&H379) = 56 Then For i = 1 To 15 Out &H378, 4 Out &H378, 5 Wait 5 Next i End If i = 1 While i < 90 And Inp(&H379) = 120 Out &H378, 6 Out &H378, 7 Wait 5 i = i + 1 Wend If i = 90 Then MsgBox "Initialization failed. Please check all the cables and power supply and press [Initialize] button.", vbCritical, "Error... Initialization Failed" Exit Sub Else For i = 1 To 80 Out &H378, 4 Out &H378, 5 Wait 5 Next i Form1.shpSample.Left = 800 CPx = 0 txtZ.Text = 0 End If

End Sub

Private Sub Timer2_Timer() If DKey = 2 And CPz < 80 Then Out &H378, 10 Out &H378, 11 Form1.shpSample.Top = Form1.shpSample.Top + 10 CPz = CPz + 1 txtZ.Text = CPz End If If DKey = 0 And CPz > 0 Then Out &H378, 8

314 Out &H378, 9 Form1.shpSample.Top = Form1.shpSample.Top - 10 CPz = CPz - 1 txtZ.Text = CPz End If If DKey = 3 And CPx < 80 Then Out &H378, 6 Out &H378, 7 Form1.shpSample.Left = Form1.shpSample.Left - 10 CPx = CPx + 1 txtX.Text = CPx End If If DKey = 1 And CPx > 0 Then Out &H378, 4 Out &H378, 5 Form1.shpSample.Left = Form1.shpSample.Left + 10 CPx = CPx - 1 txtX.Text = CPx End If

End Sub

Sub GoPos(X As Integer, z As Integer) Dx = X - CPx Dz = z - CPz If Dx > 0 Then For i = 1 To Dx Out &H378, 6 Out &H378, 7 Form1.shpSample.Left = Form1.shpSample.Left - 10 CPx = CPx + 1 If CPx > 80 Then Exit Sub txtX.Text = CPx DoEvents Wait 5 Next i End If

If Dx < 0 Then For i = 1 To Abs(Dx) Out &H378, 4 Out &H378, 5 Form1.shpSample.Left = Form1.shpSample.Left + 10 CPx = CPx - 1 If CPx < 0 Then Exit Sub txtX.Text = CPx DoEvents Wait 5 Next i End If

If Dz > 0 Then For i = 1 To Dz Out &H378, 10 Out &H378, 11 Form1.shpSample.Top = Form1.shpSample.Top + 10 CPz = CPz + 1

315 If CPz > 80 Then Exit Sub txtZ.Text = CPz DoEvents Wait 5 Next i End If

If Dz < 0 Then For i = 1 To Abs(Dz) Out &H378, 8 Out &H378, 9 Form1.shpSample.Top = Form1.shpSample.Top - 10 CPz = CPz - 1 If CPz < 0 Then Exit Sub txtZ.Text = CPz DoEvents Wait 5 Next i

End If

End Sub

*********************************************************************** module1.bas *********************************************************************** ‘Copyrights – Viraj Jayaweera Piyankarage, Optoelectronics Lab of Georgia State University

Public Declare Function GetKeyState Lib "user32" _ (ByVal nVirtKey As Long) As Integer Public Const KeyDown As Long = -128 Sub Wait(Time_in_ms As Integer) st = Timer While Timer - st < Time_in_ms / 1000 DoEvents Wend End Sub

316 Appendix C

Microsoft Excel macro programs development for data file manipulation

C.1 I-V-T data import and Arrhenius data extracting

The following two macro programs helps the user to import and plot multiple data files generated from the I-V-T measurement program (under the option “Save As ASCII text file”) and extract

Arrhenius data (See Appendix A). Figure C.1 shows the customized Excel menu items so that user can easily access the macro programs.

317

318 C.1.1 Excel macro source code

Sub OpenIVT() ' Macro written by Viraj Jayaweera Piyankarage 1/29/2006 ' To open IVT Ascii files on excel workbook

Dim fnames As Variant On Error GoTo ErrHandler nl = Chr(10) & Chr(13)

fnames = Application.GetOpenFilename("txt Files (*.txt), *.txt", , , , MultiSelect:=True) temp = fnames(1) For i = 1 To UBound(fnames) - 1 fnames(i) = fnames(i + 1) Next i fnames(UBound(fnames)) = temp

Counter = 1 c = ActiveCell.Column Workbooks.Add Range("A1").Select NewBook = ActiveWorkbook.Name

While Counter <= UBound(fnames)

Workbooks.OpenText Filename:= _ fnames(Counter), Origin:=932, _ StartRow:=1, DataType:=xlDelimited, TextQualifier:=xlDoubleQuote, _ ConsecutiveDelimiter:=False, Tab:=True, Semicolon:=False, Comma:=True, _ Space:=False, Other:=False, FieldInfo:=Array(Array(1, 1), Array(2, 1), Array( _ 3, 1)), TrailingMinusNumbers:=True Nname = ActiveWorkbook.Name Columns("A:B").Select Selection.Copy Windows(NewBook).Activate ActiveSheet.Paste c = ActiveCell.Column c = c + 2

' ***************convert to Absoloute value******************* ActiveCell.SpecialCells(xlLastCell).Select r = ActiveCell.Row Range(Cells(20, c), Cells(20, c)).Select ActiveCell.FormulaR1C1 = "=ABS(RC[-1])"

319 Selection.AutoFill Destination:=Range(Cells(20, c), Cells(r, c)) Range(Cells(20, c), Cells(r, c)).Select Selection.Copy Range(Cells(20, c - 1), Cells(20, c - 1)).Select Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _ :=False, Transpose:=False Range(Cells(20, c), Cells(20, c)).Select Range(Selection, Selection.End(xlDown)).Select Application.CutCopyMode = False Selection.ClearContents ' ***********************************************

Range(Cells(1, c), Cells(1, c)).Select Windows(Nname).Activate ActiveWorkbook.Close Counter = Counter + 1 Wend Windows(NewBook).Activate ActiveCell.SpecialCells(xlLastCell).Select Selection.End(xlToLeft).Select r = ActiveCell.Row

Range("A20:B20").Select Range(Selection, Selection.End(xlDown)).Select Charts.Add ActiveChart.ChartType = xlXYScatterSmoothNoMarkers rr = "A20:B" & Trim(r) ActiveChart.SetSourceData Source:=Sheets("Sheet1").Range(rr), PlotBy _ :=xlColumns ActiveChart.Location Where:=xlLocationAsNewSheet With ActiveChart .HasTitle = False .Axes(xlCategory, xlPrimary).HasTitle = True .Axes(xlCategory, xlPrimary).AxisTitle.Characters.Text = "Voltage (V)" .Axes(xlValue, xlPrimary).HasTitle = True .Axes(xlValue, xlPrimary).AxisTitle.Characters.Text = "Current (A)" .SeriesCollection(1).Name = "=Sheet1!R18C2"

End With Sheets("Chart1").Select ActiveChart.PlotArea.Select For Counter = 2 To UBound(fnames) ActiveChart.SeriesCollection.NewSeries cc = (Counter * 2) - 1 xr = "=Sheet1!R20C" & Trim(cc) & ":R" & Trim(r) & "C" & Trim(cc)

320 yr = "=Sheet1!R20C" & Trim(cc + 1) & ":R" & Trim(r) & "C" & Trim(cc + 1) nr = "=Sheet1!R18C" & Trim(cc + 1) ActiveChart.SeriesCollection(Counter).XValues = xr ActiveChart.SeriesCollection(Counter).Values = yr ActiveChart.SeriesCollection(Counter).Name = nr Next Counter ErrHandler:

End Sub

Sub ArrheniusCalculation() ' ' ArrheniusCalculation Macro ' Macro written 2/11/2006 by Viraj Jayaweera Piyankarage

' Sheets("Sheet2").Select Range("A1").Select i = 1 If ActiveCell.Value <> "Arrhenius data extract from Sheet 1 IVT data" Then ActiveCell.FormulaR1C1 = "Arrhenius data extract from Sheet 1 IVT data" Range("A3").Select ActiveCell.FormulaR1C1 = "Temparature (K)" Range("A4").Select

Else

While Val(Range(Cells(4, i), Cells(4, i)).Value) <> 0 i = i + 1 Wend i = i - 1 Range(Cells(4, i), Cells(4, i)).Select End If Sheets("Sheet1").Select

c1 = ActiveCell.Column r1 = ActiveCell.Row V1 = ActiveCell.Value

I1 = Range(Cells(r1, c1 + 1), Cells(r1, c1 + 1)).Value T1 = Range(Cells(18, c1 + 1), Cells(18, c1 + 1)).Value

Sheets("Sheet2").Select Range(Cells(3, i + 1), Cells(3, i + 1)).Value = "Bias V " & V1 c2 = ActiveCell.Column

321 r2 = ActiveCell.Row

If c2 = 1 Then Range(Cells(r2, c2), Cells(r2, c2)).Value = T1 Range(Cells(r2, c2 + 1), Cells(r2, c2 + 1)).Value = I1 ElseIf Range(Cells(r2, 1), Cells(r2, 1)).Value = T1 Then Range(Cells(r2, c2 + 1), Cells(r2, c2 + 1)).Value = I1 End If

Sheets("Sheet1").Select

Oldc1 = c1 Do Cells.Find(What:=ActiveCell.Value, After:=ActiveCell, LookIn:=xlValues, LookAt _ :=xlWhole, SearchOrder:=xlByColumns, SearchDirection:=xlNext, MatchCase:= _ False, SearchFormat:=False).Activate

c1 = ActiveCell.Column r1 = ActiveCell.Row If r1 > 19 Then I1 = Range(Cells(r1, c1 + 1), Cells(r1, c1 + 1)).Value T1 = Range(Cells(18, c1 + 1), Cells(18, c1 + 1)).Value Sheets("Sheet2").Select r2 = r2 + 1

Sheets("Sheet1").Select End If Loop While c1 > Oldc1

End Sub

322 C.2 FT-IR Spectrum data import and responsivity calculation

The following two macro programs helps user to import and plot multiple data files generated form

I-V-T measurement program (under the option save as ASCII text file) and extract Arrhenius data

(See appendix A). Figure C.2 shows the customized Excel menu items so that user can easily access macro programs.

323

324 C.2.1 Excel macro source code

‘********************************************************************** Sub FormatWorkSheet() ‘********************************************************************** ' FormatWorkSheet Macro ' Macro recorded 7/8/2005 by Viraj Jayaweera Piyankarage ' ' Sheets.Add Sheets(1).Select Sheets(1).Name = "Raw data" Sheets(2).Select Sheets(2).Name = "Response data" Sheets(3).Select Sheets(3).Name = "NF" Sheets(4).Select Sheets(4).Name = "Bolometer"

Sheets("Raw data").Select ActiveCell.FormulaR1C1 = "Wavenumber (cm-1)" With ActiveCell.Characters(Start:=1, Length:=14).Font .Name = "Arial" .FontStyle = "Regular" .Size = 10 .Strikethrough = False .Superscript = False .Subscript = False .OutlineFont = False .Shadow = False .Underline = xlUnderlineStyleNone .ColorIndex = xlAutomatic End With With ActiveCell.Characters(Start:=15, Length:=2).Font .Name = "Arial" .FontStyle = "Regular" .Size = 10 .Strikethrough = False .Superscript = True .Subscript = False .OutlineFont = False .Shadow = False .Underline = xlUnderlineStyleNone .ColorIndex = xlAutomatic End With

325 With ActiveCell.Characters(Start:=17, Length:=1).Font .Name = "Arial" .FontStyle = "Regular" .Size = 10 .Strikethrough = False .Superscript = False .Subscript = False .OutlineFont = False .Shadow = False .Underline = xlUnderlineStyleNone .ColorIndex = xlAutomatic End With Columns("A:A").Select Columns("A:A").EntireColumn.AutoFit Range("A1:A2").Select With Selection.Interior .ColorIndex = 38 .Pattern = xlSolid End With Range("B1").Select ActiveCell.FormulaR1C1 = "Wavelength (um)" Columns("B:B").Select Columns("B:B").EntireColumn.AutoFit Range("B1:B2").Select With Selection.Interior .ColorIndex = 40 .Pattern = xlSolid End With Range("A1:B2").Select Selection.Borders(xlDiagonalDown).LineStyle = xlNone Selection.Borders(xlDiagonalUp).LineStyle = xlNone With Selection.Borders(xlEdgeLeft) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeTop) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeBottom) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With

326 With Selection.Borders(xlEdgeRight) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlInsideVertical) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With Range("A3").Select

Sheets("Bolometer").Select ActiveCell.FormulaR1C1 = "Wavenumber (cm-1)" Range("A1").Select ActiveCell.FormulaR1C1 = "Wavenumber (cm-1)" With ActiveCell.Characters(Start:=1, Length:=14).Font .Name = "Arial" .FontStyle = "Regular" .Size = 10 .Strikethrough = False .Superscript = False .Subscript = False .OutlineFont = False .Shadow = False .Underline = xlUnderlineStyleNone .ColorIndex = xlAutomatic End With With ActiveCell.Characters(Start:=15, Length:=2).Font .Name = "Arial" .FontStyle = "Regular" .Size = 10 .Strikethrough = False .Superscript = True .Subscript = False .OutlineFont = False .Shadow = False .Underline = xlUnderlineStyleNone .ColorIndex = xlAutomatic End With With ActiveCell.Characters(Start:=17, Length:=1).Font .Name = "Arial" .FontStyle = "Regular" .Size = 10 .Strikethrough = False

327 .Superscript = False .Subscript = False .OutlineFont = False .Shadow = False .Underline = xlUnderlineStyleNone .ColorIndex = xlAutomatic End With Columns("B:B").Select Columns("A:A").EntireColumn.AutoFit Range("A1").Select With Selection.Interior .ColorIndex = 38 .Pattern = xlSolid End With Range("B1").Select ActiveCell.FormulaR1C1 = "Wavelength" Columns("B:B").Select Columns("B:B").EntireColumn.AutoFit ActiveCell.FormulaR1C1 = "Wavelength (um)" Range("B1").Select Columns("B:B").EntireColumn.AutoFit With Selection.Interior .ColorIndex = 40 .Pattern = xlSolid End With Range("C1").Select Selection.Interior.ColorIndex = 4 ActiveCell.FormulaR1C1 = "Bolometer Raw data" Range("D1").Select ActiveCell.FormulaR1C1 = "NDF filter T%" Selection.Interior.ColorIndex = 37 Range("E1").Select ActiveCell.FormulaR1C1 = "Si Filter T%" Selection.Interior.ColorIndex = 45

Range("F1").Select ActiveCell.FormulaR1C1 = "Bolometer Corected Energy" Selection.Interior.ColorIndex = 4

Range("D1").Select Selection.Interior.ColorIndex = 37 Range("E1").Select Selection.Interior.ColorIndex = 45

Columns("C:F").EntireColumn.AutoFit

328 Range("A1:F1").Select Selection.Borders(xlDiagonalDown).LineStyle = xlNone Selection.Borders(xlDiagonalUp).LineStyle = xlNone With Selection.Borders(xlEdgeLeft) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeTop) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeBottom) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeRight) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlInsideVertical) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With Range("A2").Select

Sheets("NF").Select Range("A1").Select Range("A1").Value = "Rd= Dinamic Resistance of the sample" Range("A2").Value = "Rl= Load resistance" Range("A3").Value = "S= Sensitivity" Range("A4").Value = "GF= gain factor (1/(1-Cos(Q))" Range("A5").Value = "GA=Preamp Gain (200=1)" Range("A6").Value = "Req= equlent resistor" Range("A7").Value = "" Range("A8").Value = "NF=S * GF/Req" Range("A10").Select ActiveCell.FormulaR1C1 = "Bias (V)" Range("B10").Select ActiveCell.FormulaR1C1 = "Rd (ohm)" Range("C10").Select ActiveCell.FormulaR1C1 = "Rl (ohm)"

329 Range("D10").Select ActiveCell.FormulaR1C1 = "S (V/W)" Range("E10").Select ActiveCell.FormulaR1C1 = "GF" Range("F10").Select ActiveCell.FormulaR1C1 = "GA" Range("G10").Select ActiveCell.FormulaR1C1 = "Req (ohm)" Range("H10").Select ActiveCell.FormulaR1C1 = "NF" Range("A10:H10").Select With Selection .HorizontalAlignment = xlCenter .VerticalAlignment = xlBottom .WrapText = False .Orientation = 0 .AddIndent = False .IndentLevel = 0 .ShrinkToFit = False .ReadingOrder = xlContext .MergeCells = False End With Selection.Borders(xlDiagonalDown).LineStyle = xlNone Selection.Borders(xlDiagonalUp).LineStyle = xlNone With Selection.Borders(xlEdgeLeft) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeTop) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeBottom) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeRight) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlInsideVertical) .LineStyle = xlContinuous

330 .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Interior .ColorIndex = 35 .Pattern = xlSolid End With Range("A11:G20").Select With Selection.Interior .ColorIndex = 40 .Pattern = xlSolid End With Selection.Borders(xlDiagonalDown).LineStyle = xlNone Selection.Borders(xlDiagonalUp).LineStyle = xlNone With Selection.Borders(xlEdgeLeft) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeTop) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeBottom) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeRight) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlInsideVertical) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlInsideHorizontal) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With Range("H11:H20").Select With Selection.Interior

331 .ColorIndex = 34 .Pattern = xlSolid End With Selection.Borders(xlDiagonalDown).LineStyle = xlNone Selection.Borders(xlDiagonalUp).LineStyle = xlNone With Selection.Borders(xlEdgeLeft) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeTop) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeBottom) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlEdgeRight) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With With Selection.Borders(xlInsideHorizontal) .LineStyle = xlContinuous .Weight = xlThin .ColorIndex = xlAutomatic End With Range("A10:H10").Select Selection.Font.Bold = True Columns("G:G").ColumnWidth = 8.86

Range("D11").Select ActiveCell.FormulaR1C1 = "300000" Range("E11").Select ActiveCell.FormulaR1C1 = "3.4142" Range("G11").Select ActiveCell.FormulaR1C1 = "=RC[-4]*RC[-5]/(RC[-4]+RC[-5])" Range("H11").Select ActiveCell.FormulaR1C1 = "=(RC[-4]*RC[-3])/(RC[-1]*RC[-2])" Range("G11:H11").Select Selection.AutoFill Destination:=Range("G11:H20"), Type:=xlFillDefault Range("G11:H20").Select Range("D11:F11").Select

332 Selection.AutoFill Destination:=Range("D11:F20"), Type:=xlFillDefault Range("D11:F20").Select Range("F22").Select

Range("A11").Select Sheets("Raw data").Select

End Sub

‘********************************************************************** Sub OpenSpectrum() ‘**********************************************************************

' OpenSpectrum Macro ' Macro written 7/8/2005 by Viraj Jayaweera Piyankarage ' To open spectrum Ascii files on excel workbook

Dim fnames As Variant On Error GoTo ErrHandler nl = Chr(10) & Chr(13)

If Sheets(1).Name <> "Raw data" Then cho = MsgBox("This Work book not formated to Spectrum Response Calculations." & nl & "Would you like to convert this?", vbYesNo, "Work Book Format!") If cho = 6 Then FormatWorkSheet Sheets("Raw Data").Select End If End If

If Range("A3").Value = "" Then Range("A1").Select Selection.Interior.ColorIndex = 38 ActiveCell.FormulaR1C1 = "Wavenumber (cm-1)" ActiveCell.Characters(Start:=15, Length:=2).Font.Superscript = True Range("B1").Select Selection.Interior.ColorIndex = 36 ActiveCell.FormulaR1C1 = "Wavelength (um)" Range("c2").Select

Else Range("B3").Select n = 3

333 While ActiveCell.FormulaR1C1 <> "" Range(Cells(3, n), Cells(3, n)).Select n = n + 1 Wend End If fnames = Application.GetOpenFilename("Ascii Files (*.asc), *.asc", , , , MultiSelect:=True) temp = fnames(1) For i = 1 To UBound(fnames) - 1 fnames(i) = fnames(i + 1) Next i fnames(UBound(fnames)) = temp

Counter = 1 c = ActiveCell.Column

While Counter <= UBound(fnames) Open fnames(Counter) For Input As #1 r = 3 For i = 1 To 9 Input #1, a$ Next i Range(Cells(1, c), Cells(1, c)).Select Selection.Interior.ColorIndex = 35 Range(Cells(1, c), Cells(1, c)).Value = "(" & Chr$(62 + c) & ") " & a$ Range(Cells(2, c), Cells(2, c)).Value = "(" & Chr$(94 + c) & ") " For i = 1 To 75 Input #1, a$ Next i If c = 3 Then While Not EOF(1) Range(Cells(r, 1), Cells(r, 1)).Value = Val(Left(a$, 12)) Range(Cells(r, c), Cells(r, c)).Value = Val(Mid(a$, 12, Len(a$))) Input #1, a$ r = r + 1 Wend Range("B3").FormulaR1C1 = "=10000/RC[-1]" Range("B3").Select Selection.AutoFill Destination:=Range(Cells(3, 2), Cells(r - 2, 2))

Else While Not EOF(1) Range(Cells(r, c), Cells(r, c)).Value = Val(Mid(a$, 12, Len(a$))) Input #1, a$ r = r + 1 Wend

334 End If Close #1 'Range(Cells(1, c), Cells(1, c)).EntireColumn.AutoFit c = c + 1 Counter = Counter + 1 Wend MsgBox "Done" ErrHandler:

End Sub

‘********************************************************************** Sub OpenBolometer() ‘**********************************************************************

' Macro written 7/8/2005 by Viraj Jayaweera Piyankarage ' To open Bolometer data Ascii files on excel workbook

Dim fnames As Variant ' On Error GoTo ErrHandler nl = Chr(10) & Chr(13)

If Range("A2").Value = "" Then Range("A1").Select Selection.Interior.ColorIndex = 38 ActiveCell.FormulaR1C1 = "Wavenumber (cm-1)" ActiveCell.Characters(Start:=15, Length:=2).Font.Superscript = True Range("B1").Select Selection.Interior.ColorIndex = 36 ActiveCell.FormulaR1C1 = "Wavelength (um)" Range("c2").Select

Else Range("A2").Select End If

335 fname = Application.GetOpenFilename("Ascii Files (*.asc), *.asc", , , , MultiSelect:=False) Close All Open fname For Input As #1 r = 2 For i = 1 To 9 Input #1, a$ Next i Range(Cells(1, 3), Cells(1, 3)).Select Selection.Interior.ColorIndex = 35 Range(Cells(1, 3), Cells(1, 3)).Value = "Bolometer " & a$

For i = 1 To 75 Input #1, a$ Next i

While Not EOF(1) Range(Cells(r, 1), Cells(r, 1)).Value = Val(Left(a$, 12)) Range(Cells(r, 3), Cells(r, 3)).Value = Val(Right(a$, 8)) Input #1, a$ r = r + 1 Wend

Range("B2").FormulaR1C1 = "=10000/RC[-1]" Range("B2").Select Selection.AutoFill Destination:=Range(Cells(2, 2), Cells(r - 1, 2))

Close #1 Range(Cells(1, 3), Cells(1, 3)).EntireColumn.AutoFit

ErrHandler:

End Sub

‘********************************************************************** Sub PlotRawSpectrum() ‘**********************************************************************

Range("A2").Select ' Sheets("Raw data").Select Range(Selection, Selection.End(xlToRight)).Select Range(Selection, Selection.End(xlDown)).Select Charts.Add ActiveChart.ApplyCustomType ChartType:=xlUserDefined, TypeName:= _ "Raw Spectrum cm-1" ActiveChart.SetSourceData Source:=Sheets("Raw data").Range("A1:I8502"), _ PlotBy:=xlColumns

336 ActiveChart.SeriesCollection(1).Delete ActiveChart.Location Where:=xlLocationAsObject, Name:="Raw data" With ActiveChart .HasTitle = True .ChartTitle.Characters.Text = "Raw spectrum of the sample " .Axes(xlCategory, xlPrimary).HasTitle = True .Axes(xlCategory, xlPrimary).AxisTitle.Characters.Text = _ "Wavenumber (cm-1)" .Axes(xlValue, xlPrimary).HasTitle = True .Axes(xlValue, xlPrimary).AxisTitle.Characters.Text = "Energy" End With

End Sub

Sub ResponseCal()

Sheets("Raw data").Select Rows("1:2").Select Selection.Copy Sheets("Response data").Select Range("A1").Select ActiveSheet.Paste Range("C3").Select Application.CutCopyMode = False ActiveCell.FormulaR1C1 = "='Raw data'!RC*NF!R11C8/Bolometer!R[-1]C6" Range("C4").Select Sheets("Raw data").Select Range("A3:B3").Select Range(Selection, Selection.End(xlDown)).Select Selection.Copy Sheets("Response data").Select Range("A3").Select ActiveSheet.Paste Range("A3").Select

End Sub

337

338

Public fNameBack As Variant Public fNameSamp As Variant Public BData As Variant Public NoData As Long

Private Sub cmdBrowsBack_Click() fNameBack = Application.GetOpenFilename("Ascii Files (*.asc), *.asc", , , , MultiSelect:=False) txtBack.Text = fNameBack Open fNameBack For Input As #1 For i% = 1 To 86 Input #1, X Next i% NoData = Val(X) ReDim BData(1 To NoData, 1 To 2) While Not EOF(1) And X <> "#DATA" Input #1, X Wend For i% = 1 To NoData Input #1, X, Y BData(i%, 1) = X If Y = 0 Then Y = 0.000001 BData(i%, 2) = Y Next i% Close #1 End Sub

Private Sub cmdBrowsSamp_Click() fNameSamp = Application.GetOpenFilename("Ascii Files (*.asc), *.asc", , , , MultiSelect:=True) temp = fNameSamp(1) For i% = 1 To UBound(fNameSamp) - 1 fNameSamp(i%) = fNameSamp(i% + 1) Next i% fNameSamp(UBound(fNameSamp)) = temp

i% = 1 While i% <= UBound(fNameSamp) txtSamp.Text = txtSamp.Text & fNameSamp(i%) & "," i% = i% + 1 Wend End Sub

Private Sub cmdCalc_Click() pgb1.Value = 1

339 UserForm1.MousePointer = fmMousePointerHourGlass If Range("A2").Value = "" And fNameBack <> "" Then Range("A1").Select Selection.Interior.ColorIndex = 38 ActiveCell.FormulaR1C1 = "Wavenumber (cm-1)" ActiveCell.Characters(Start:=15, Length:=2).Font.Superscript = True Range("B1").Select Selection.Interior.ColorIndex = 36 ActiveCell.FormulaR1C1 = "Wavelength (um)" Range("c2").Select For n = 1 To NoData Range(Cells(n + 1, 1), Cells(n + 1, 1)).Value = BData(n, 1) Next n r = n + 1 Range("B2").FormulaR1C1 = "=10000/RC[-1]" Range("B2").Select Selection.AutoFill Destination:=Range(Cells(2, 2), Cells(r - 1, 2)) Range(Cells(1, 1), Cells(1, 2)).EntireColumn.AutoFit End If c = 1 While Range(Cells(2, c), Cells(2, c)).Value <> "" c = c + 1 Wend If txtSamp.Value <> "" Then nf% = 1 While nf% <= UBound(fNameSamp) Open fNameSamp(nf%) For Input As #1 r = 2 For i% = 1 To 9 Input #1, X Next i% Range(Cells(1, c), Cells(1, c)).Select Selection.Interior.ColorIndex = 35 Range(Cells(1, c), Cells(1, c)).Value = "(" & Chr$(62 + c) & ") " & X While Not EOF(1) And X <> "#DATA" Input #1, X Wend For i% = 1 To NoData Input #1, X, Y Range(Cells(r, c), Cells(r, c)).Value = Y * 100 / BData(i%, 2) r = r + 1 Next i% pgb1.Value = nf% * 100 / UBound(fNameSamp) nf% = nf% + 1 c = c + 1 Close #1

340

Wend c = c + 1 End If UserForm1.MousePointer = fmMousePointerDefault End Sub

Private Sub cmdClose_Click() UserForm1.Hide End Sub

341